GIFT  OF 
Dean  Frank  H.    Probert 


Sold  hv  Rnnk 


TIMBERING   AND  MINING 


Published    by  the 

McGraw-Hill    Book.  Company 


Successors  to  tKe  Book  Departments  of  tKe 

McGraw  Publishing  Company  Hill  Publishing;  Company 

Publishers   of  Books  for 

Electrical  World  The  Engineering  and  Mining  Journal 

The  Engineering  Record  Power  and  The  Engineer 

Electric  Railway  Journal  American   Machinist 


TIMBERING    AND 

MINING 


A  TREATISE  ON  PRACTICAL  AMERICAN 
METHODS 


BY 

WILLIAM    H.  STORMS,  E.M. 


McGRAW-HILL  BOOK  COMPANY 

239  WEST   39TH   STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.G. 

1909 


Copyright,  1909,  BY  THE  HILL  PUBLISHING  COMPANY 


S8 

CxT- 

p     .       ! 

DE?I. 


01 

DEAN  FftANK  H  P*i03EftT 

MINING  DEPI. 


INTRODUCTION 

THE  author  of  this  series  of  papers  on  Practical  Mining  Methods 
and  Timbering  of  mine  workings  has  undertaken  the  task  with 
the  full  knowledge  that  whatever  may  be  said  herein  to-day, 
is  more  than  likely  to  become  ancient  history  within  a  very 
few  years. 

In  1892  the  writer  prepared  a  little  volume  entitled  "Methods 
of  Mine  Timbering,"  which  was  issued  in  1893  as  Bulletin  No.  2 
in  the  series  of  publications  of  the  State  Mining  Bureau  of  Cali- 
fornia. That  little  work  was  evidently  appreciated  by  the  mining 
men  of  the  country,  for  the  large  edition  was  exhausted  within 
a  few  months.  It  had  the  distinction  of  being  the  first  mono- 
graph on  the  subject,  and  was  republished  in  many  mining, 
engineering  and  scientific  papers  throughout  the  world,  in  English, 
French,  and  German,  usually  with  full  credit  to  both  the  State 
Mining  Bureau  of  California,  and  to  the  author.  So  great  was 
the  demand  for  it  that  in  1894  a  second  edition,  enlarged  slightly 
and'  somewhat  improved,  was  published,  and  this,  like  the  first 
edition,  was  promptly  absorbed.  In  time  the  treatise,  issued  as 
a  gratuitous  contribution  to  mining  literature  by  the  State  of 
California,  found  ready  sale.  Few  copies  are  seen  now,  as  they 
have  gone  largely  into  private  libraries.  Since  this  work  became 
unobtainable,  there  has  been  an  almost  constant  demand  for  it, 
and  even  to-day,  after  a  lapse  of  fifteen  years,  there  are  many 
calls  for  "Methods  of  Mine  Timbering." 

The  writer  has  therefore  prepared  a  second  treatise  on  the 
subject  in  the  belief  that  it  will  meet  with  as  kind  a  reception 
as  the  original.  That  was  devoted  almost  exclusively  to  methods 
of  timbering  mine  workings,  but  in  the  years  that  have  passed 
since  1892  the  constantly  increasing  cost  of  timber  in  almost 
every  mining  region  has  led  mining  engineers  to  devise  methods 
of  removing  ore  from  underground  workings,  with  expedition 
and  safety,  while  employing  a  minimum  amount  of  timber. 
Mining  methods,  therefore,  will  receive  a  large  share  of  attention 


vi  INTRODUCTION 

in  these  papers  as  well  as  methods  of  framing  and  placing  timbers 
in  mine  excavations. 

Like  the  original,  it  is  the  intention  to  make  this  new  work 
practical,  and  illustrative  of  those  methods  which  in  various 
parts  of  the  world  have  been  applied  with  success.  A  few  sug- 
gestions will  also  be  offered  as  to  methods  of  mining  under  some 
of  the  conditions  not  commonly  met. 

This  work  is  not  for  the  enlightenment  of  those  who  are 
experienced  and  therefore  in  no  need  of  such  a  treatise,  but  rather 
for  those  who  feel  the  need  of  a  work  which  will  give  them  prac- 
tical ideas  of  what  should  be  done  under  given  conditions  in 
mining,  and  how  to  do  it.  If  this  aim  is  attained,  the  author 
will  feel  that  he,  with  the  assistance  of  others,  has  published  a 
work  which  shall  long  have  practical  value  as  a  standard  expo- 
nent of  the  best  mining  practice  in  the  early  part  of  the  twentieth 
century.  Probably,  too,  if  a  copy  of  this  work  is,  three  hundred 
years  from  now,  still  in  existence,  it  will  be  as  great  a  curiosity 
then  as  is  the  work  of  Agricola  to  us  now. 


CONTENTS 

CHAP.  PAGE 

INTRODUCTION v 

I.     TIMBER  USED  IN  MINING 1 

II.     PRESERVATION  OF  TIMBERS 8 

III.  DRIFTING  AND  DRIFT  SETS      ..........  16 

Driving  lagging  in  drifting 24 

IV.  DRIVING  IN  RUNNING  GROUND     .      .     .   ' 28 

Breast  boards 29 

V.  STRUCTURAL  STEEL  IN  MINE  WORKINGS 34 

VI.  TIMBERING  DRIFT  GRAVEL  MINES  IN  CALIFORNIA  ...  38 

Breasting  posts  and  caps 38 

VII.  SHAFTS 42 

Location,  kind  and  size  of  shafts.  Substantial  timbering 

usually  necessary 42 

Prospecting  shafts  in  good  ground  and  those  requiring  close 

timbering.  Cribs  and  single -compartment  shafts  ...  46 

Size  and  division  of  working  shafts.  Drainage  ....  49 

Positions  of  temporary  hoisting  plant  and  permanent  plant  52 

Size  of  shaft  compartments ' 54 

The  collar  55 

Hanging-bolts      •..,.      .      .      .      .      .      .      .      .      .      .      .  58 

The  cross-head  in  sinking  shafts  with  a  bucket     ....  58 

Stull  methods  in  many  small  mines  of  the  Cobalt  district, 

Ontario 62 

VIII.  BUCKET  DUMPING 64 

Methods  at  vertical  shafts 64 

Methods  at  inclined  shafts 69 

IX.  FRAMING  SHAFT  TIMBERS 73 

Framing  for  vertical  shafts 75 

The  divider  and  spliced  wall  plate -.-.*•'.  80 

The  template •  .  85 

Handling  timbers  in  shafts ...  .  .  85 

Some  useful  knots 88 

Placing  timbers  of  shaft  sets  in  position 89 

Placing  timbers  in  inclined  shafts  and  lining  the  sets  .  .  93 

Difficulties  in  sinking  through  running  ground  ....  96 

Sinking  through  running  or  loose  ground  .  .  .  ,  . .  .  97 

Combination  vertical  and  inclined  shafts 102 

X.  BEARERS  IN  SHAFTS 105 

Fenders  for  the  protection  of  shaft  timbers  when  blasting  .  Ill 

The  cable  mat H2 

vii 


CONTENTS 


CHAP. 


PAGE 


Extension  tracks  for  sinking 1 13 

Inverted  rails 114 

Sinking-ladders - 115 

Inclines  in  hard  rock 115 

Shaft  repairing 116 

XI.     POSITION  AND  DIRECTION  OF  DRILL  HOLES  IN  SHAFT  SINKING  117 

XII.     CUTTING  AND  TIMBERING  STATIONS  AT  SHAFTS      .      .      .      .  119 

Ore  pockets  beneath  the  levels         120 

Types  of  stations  at  inclined  and  vertical  shafts  .      .      .      .  125 

Drainage  by  means  of  skips  and  tanks 125 

XIII.  MINING  LARGE  ORE  BODIES  BY  THE  OPEN-CUT  OR  "GLORY- 

HOLE  "  SYSTEM 133 

The  churn-drill  or  jumper 141 

The  steam  shovel  in  open  cuts 144 

XIV.  THE  OVERHAND  AND  UNDERHAND  METHODS  OF  STOPING  VEINS  148 
XV.     UNUSUAL  METHODS  OF  STOPING  ENFORCED  BX  SCARCITY  OF 

TIMBER 154 

XVI.     STOPING  IN  FLAT  OR  LOW-LYING  VEINS 158 

XVII.     RAISES  FOR  CONNECTION  OF  LEVELS 161 

XVIII.     STOPING  AND  FILLING  IN  A  MINE  HAVING  WEAK  WALLS      .  166 
XIX.     THE  CAVING  SYSTEM  PRACTISED  AT  THE  PEWABIC  MINE,  IRON 

MOUNTAIN,  MICHIGAN 172 

XX.     STOPING  IN  SWELLING  GROUND 178 

Main  gangways  driven  in  the  country  rock 179 

Connecting  levels  when  stoping  veins  of  moderate  width     .  184 

XXI.     STOPING  LARGE  ORE  BODIES 187 

Introduction  of  the  square-set  by  Philip  Deidesheimer  on 

the  Comstock 188 

Usefulness  of  the  square-set  in  extracting  large  ore  bodies  191 

Mistakes  made  in  using  the  square-set        .......  193 

XXII.     FRAMING  SQUARE-SET  TIMBERS 197 

Construction  of  the  square-set  in  the  stope 201 

XXIII.  MODIFICATIONS  OF  THE  SQUARE-SET  SYSTEM  IN  CALIFORNIA 

MINES -205 

Construction  of  chutes  in  square-sets 211 

XXIV.  STOPING  LARGE   ORE   BODIES   BY   THE   BLOCK   SYSTEM   AT 

BROKEN  HILL,  NEW  SOUTH  WALES 213 

Underground  open-cut  and  sloping-stope  systems,  at  Broken 

Hill 218 

XXV.  MINING  AT  THE  HOMESTAKE,  LEAD,  SOUTH  DAKOTA  .  .  t  229 

Stoping  without  timbers  at  the  Homestake 238 

Usefulness  of  mine  models .  .  .243 

XXVI.  WORKING  DANGEROUS  GROUND  IN  THE  KIMBERLEY  DIAMOND 

MINES 247 

XXVII.  THE  DELPRAT  METHOD  OF  STOPING  WITHOUT  TIMBERS     .      .  253 
XXVIII.  HEAD-FRAMES  255 


CHAPTER  I 

TIMBER  USED   IN   MINING 

MINERS  throughout  the  Western  United  States  prefer,  as  a 
rule,  those  kinds  of  timber  commonly  known  as  spruce  and 
Oregon  pine,  the  latter  being  really  what  is  technically  called 
Douglas  spruce,  though  it  is  also  variously  known  as  Douglas 
fir,  yellow  fir,  or  red  fir,  according  to  its  color.  In  addition  to 
these  two  kinds  of  timber,  yellow  pine,  sugar  pine,  pinon  (bull) 
pine,  several  varieties  of  fir,  and,  in  a  few  localities,  oak,  are 
used  for  the  support  of  mine  workings. 

In  the  Coast  Range  of  California,  redwood,  though  usually 
considered  unsuited  to  the  purpose,  has  been  extensively  em- 
ployed in  timbering  quicksilver  mines,  particularly  at  New 
Almaden,  in  Santa  Clara  County.  Redwood,  though  brittle,  is 
enduring,  and  has  been  found  to  answer  the  purpose  very  well 
indeed,  where  the  pressure  has  not  been  too  great. 

On  the  desert,  yuccas,  juniper,  cotton  wood,  scrub  pine,  old 
railroad  ties,  in  fact,  almost  any  sort  of  wood  available,  has  been 
used  by  prospectors  in  timbering  their  workings,  though  in  some 
of  these  mines  we  have  observed  that  the  timbers  had  died  out, 
and  fallen  down,  while  the  ground  still  stood  without  support. 
It  is  not  always  possible  for  miners  to  obtain  the  timber  they 
prefer,  and  therefore  they  naturally  turn  to  whatever  kind  of 
timber  may  be  available  and  least  expensive  in  their  locality. 

In  1904  an  attempt  was  made  by  the  writer  to  ascertain 
from  various  sources  what  kind  of  timber  had  been  found  most 
satisfactory  in  mine  workings,  and  with  that  idea  in  view  a  num- 
ber of  mine  superintendents  in  California  were  requested  to  give 
the  result  of  their  experience  in  this  connection.  The  replies 
disclosed  the  fact  that  all  were  not  of  one  mind  on  the  subject. 
The  information  was  desired  primarily  as  the  basis  of  a  paper 
to  be  read  before  the  California  Miners'  Association.  To  this 
end  the  following  questions  were  sent  to  each  of  the  several 

1 


TIMBERING   AND  MINING 

gentlemen  whose  replies  are  given  below.     The  questions  covered 
the  following  points: 

1.  Kind  of  timber  used;  whether  yellow  or  sugar  pine,  spruce, 
fir,  Oregon  pine,  etc. 

2.  Condition  when  placed  in  the  mine  —  seasoned  or  not. 

3.  Position  in  the  mine  with  reference  to  excavation,  that 
is,  whether  in  stope,  drift  or  shaft,  and  relation  of  air  currents, 
as  there  seems  to  be  considerable  difference  in   the  enduring 
qualities  of  timber,  depending  on  its  location  —  whether  in  still 
air  or  in  a  current  of  considerable  velocity;  and  also  whether 
the  air  current  is  pure  and  fresh  or  whether  heavily  laden  with 
carbon  dioxide  and  the  other  foul  gases  peculiar  to  mines. 

4.  Humidity  of  air;  is  the  stope  damp?     Does  fungus  form 
rapidly  on  the  timbers,  or  is  it  comparatively  dry  and  free  from 
these  growths? 

5.  How  long  should  a  timber,  say  20  to  30  in.  diameter, 
endure  under  average  conditions,  in  a  well-ventilated  drift  in  a 
damp  mine?     (a)  spruce;  (6)  yellow  pine;  (c)  sugar  pine;  (d)  fir; 
(e)  redwood. 

6.  What  is  the  best  timber  for  general  use  in  mines?     Is 
there  a  material  difference  in  the  various  kinds  of  timber,  of 
equally  good  condition,  that  is,  well-seasoned  sticks? 

To  the  questions  submitted,  Mr.  George  W.  Starr,  managing 
director  of  the  Empire  mines  at  Grass  Valley,  California,  replied 
as  follows: 

No.  1.     Yellow  pine  and  spruce. 

No.  2.     Used  after  being  cut  eight  months. 

No.  3.  We  use  yellow  pine  in  stopes  and  in  places  where  not  much  life 
of  timber  is  required.  Spruce  is  used  in  drifts  and  main  tunnels. 

No.  4.     Stopes  are  usually  damp  and  fungus  forms  after  six  months. 

No.  5.  (a)  In  wet  ground  where  water  is  trickling  over  timber  constantly, 
spruce  will  last  indefinitely,  but  in  damp  ground  three  to  five  years;  (6)  yellow 
pine,  about  two  years. 

No.  6.     Spruce. 

The  Empire  mines  are  opened  on  small  veins  with  low  dip  in  granite, 
and  present  unusual  conditions,  being  very  unlike  the  mines  of  the  Mother 
Lode  of  California. 

Mr.  John  Ross,  Jr.,  a  California  mine  manager  of  many  years' 
experience,  replied  to  the  questions  as  follows: 

No.  1.  Oak,  spruce,  yellow  pine,  Douglas  spruce  (commonly  known 
as  Oregon  pine),  bull  (pinon)  pine,  sugar  pine,  native  fir. 


TIMBER  USED   IN   MINING  3 

Oak  is  rarely  used  because  of  its  scarcity,  but  I  know  a  shaft  that  was 
sunk  in  1859-60  and  kept  open  for  seven  years,  part  of  the  shaft  being  tim- 
bered with  oak.  The  mine  then  lay  idle  for  twenty  years,  the  shaft  being 
full  of  water.  It  was  reopened  in  1887,  and  has  been  kept  open  until  the 
present  time  [1904].  The  oak  timbers  stood  until  1901,  and  at  that  time 
the  wall  plates  and  sills  were  in  perfect  condition,  and  would  not  have  been 
removed  then,  but  for  the  fact  that  the  pressure  on  the  end  timbers  —  or 
legs  —  had  been  great  enough  to  crush  the  ends  a  little,  making  them  too 
short  to  be  used  again.  The  shaft  is  an  incline,  and  a  little  water  was  con- 
stantly trickling  over  the  timbers  —  enough  to  keep  them  thoroughly  wet 
all  the  time.  Under  the  same  conditions  a  few  sets  of  bull  (pin on)  pine  in 
the  same  shaft  stood  for  forty  years,  while  spruce,  yellow  pine,  Oregon  pine 
and  fir  had  to  be  changed  several  times,  the  timber  lasting  in  the  order  given, 
its  life  in  the  shaft  being  from  two  to  eight  years,  where  the  timbers  were 
always  wet.  In  other  parts  of  the  shaft,  where  the  timbers  were  wet  and 
dry  alternately,  the  life  of  the  timber  ranged  from  two  to  three  years.  This 
shaft,  however,  is  an  exceptionally  destructive  one  to  timbers,  being  sunk 
in  the  vein  fissure  and  in  the  gouge  where  the  pressure  on  the  timbers  was 
not  equally  distributed.  In  justice  to  the  other  members  of  the  timber 
family,  it  is  but  fair  to  say  that  the  oak  and  bull  pine  were  used  in  the  nar- 
rowest part  of  the  vein,  where  the  pressure  was  not  so  great  as  where  the 
fissure  was  wider. 

No.  2.  The  condition  of  the  timbers  going  into  the  mine  varies  from 
green,  fresh  from  the  axe,  to  thoroughly  seasoned  —  that  is,  timber  that  has 
been  cut  two  years.  Where  the  timbers  going  into  the  mine  are  sound, 
and  they  are  placed  where  the  water  trickles  over  them,  there  is  practically 
no  difference  in  the  life  of  a  seasoned  timber  or  a  green  one;  but  in  a  dry 
or  damp  drift,  the  seasoned  timber  is  preferable,  partly  on  account  of  less 
cost  in  handling  and  putting  in  place;  and  furthermore  it  is  not  so  quickly 
attacked  by  either  fungus  or  dry  rot.  I  have  seen  green  timber  placed  in  a 
damp  drift  attacked  by  fungus  within  two  weeks  of  the  time  it  was  put  in 
place;  but  this  is  uncommon. 

No.  3.  The  position  of  timbers  in  the  mine  relative  to  air  currents,  and 
the  purity  of  the  air,  has  more  to  do  with  its  life,  in  my  opinion,  than  any- 
thing else.  In  making  a  connection  between  two  shafts  1000  ft.  apart,  work 
was  commenced  from  each  shaft,  the  air  being  forced  down  each  shaft  to  the 
face  of  each  drift,  giving  plenty  of  good  air  for  workmen.  The  work  was 
not  rushed,  taking  about  a  year's  time.  During  all  this  time  the  timbers 
stood  well,  showing  little  sign  of  either  dry  rot  or  fungus  growth.  When  the 
connection  was  made  the  air  came  through  the  drift  with  considerable  velocity; 
making  one  shaft  a  down-cast,  and  the  other  an  up-cast.  Near  the  down- 
cast shaft  the  drift  and  stope  were  30  ft.  wide,  and  heavily  timbered.  These 
timbers  stood  for  six  years  with  practically  no  repairs.  Between  this  place 
and  the  up-cast  shaft  the  drift  was  opened  out  to  a  width  of  20  to  30  ft.  in 
a  number  of  places  in  stoping,  the  drift  being  kept  as  straight  as  possible, 
and  through  this  most  of  the  air  came.  It  was  quickly  noted  that  the  further 
we  got  from  the  down-cast  shaft,  the  worse  the  condition  of  the  timbers 
became,  they  being  attacked  with  fungus  growth  and  dry  rot.  It  was  also 


4  TIMBERING  AND  MINING 

noticed  that  where  the  drift  had  been  widened  by  stoping,  timbers  out  of  the 
direct  line  of  the  air  current  were  not  so  quickly  attacked,  and  experience 
later  showed  that  they  would  last  twice  as  long.  The  life  of  timbers  that 
were  in  direct  line  with  the  air  current  was  from  one  to  two  years,  and  when 
not  fairly  in  the  current  from  two  to  four  years.  It  was  also  noted  that  the 
timbers  in  the  up-cast  shaft,  above  the  point  of  connection,  soon  became 
seriously  affected,  necessitating  considerable  repair  work.  As  the  property 
became  more  extensively  developed,  this  experience  was  duplicated  in  three 
different  levels. 

Subsequently,  in  opening  a  drift  in  a  caved  portion  of  one  of  these  con- 
necting levels,  where  the  drift  proper  had  been  retimbered  three  times  before 
it  caved,  it  was  found  that  the  drift  timbers  were  little  better  than  punk, 
while  the  stope  timbers  that  came  down  with  the  caving  of  the  drift  were 
as  sound  as  when  placed  in  position.  The  stope  timbers  had  been  out  of  the 
direct  line  of  the  air  current,  and  many  of  these  stope  timbers  had  been  in 
place  three  to  four  years  longer  than  those  in  the  drift. 

No.  4.  Warm,  moist  air,  in  a  mine  that  has  but  one  shaft,  is  far  more 
destructive  on  timber  than  dry  and  comparatively  cool  air.  In  the  latter 
instance,  the  timber  will  last  at  least  twice  as  long. 

No.  5.  (a)  Spruce,  about  six  years;  (6)  yellow  pine,  about  five  years; 
(c)  sugar  pine,  about  four  years;  (d)  fir,  about  two  years;  (e)  redwood  —  never 
used  any. 

No.  6.     For  all-around  work,  spruce. 

At  one  time  a  comparative  test  was  made  in  the  Wildman  mine,  at  Sutter 
Creek,  Cal.,  in  a  raise  where  the  ground  was  very  heavy.  Oregon  pine,  12  X 
12  in.,  was  used  on  one  side,  and  14-in.  round  native  yellow  pine  on  the  other. 
In  one  year  the  round,  yellow  pine  stick  was  badly  bent  and  twisted,  and 
the  legs  were  forced  into  the  wall-plate  three  inches,  but  there  was  still  strength 
enough  in  the  stick  to  hold  the  ground,  while  the  12  X  12  in.  Oregon  pine  was 
shattered  into  slivers,  and  could  bear  no  further  pressure.  None  of  the 
timbers  used  in  this  work  showed  any  rot  or  fungus  growth. 

Mr.  G.  McM.  Ross,  a  mine  manager  and  superintendent  of 
large  experience  in  the  West,  contributed  the  following  in  reply 
to  the  questions: 

No.  1.  I  have  used  many  kinds  of  timber  in  various  conditions,  from 
green,  wet  wood,  fresh  from  the  sawmill  pond,  to  old  telegraph  poles,  rail- 
road ties,  sage  brush,  and  the  juniper  of  Nevada ;  also  the  fiber  of  the  tall 
cactus  of  Arizona. 

The  above  answers  the  second  question  also. 

No.  3.  Any  timber  will  last  longer  in  a  stope  or  drift  that  is  well  ven- 
tilated with  fresh,  pure  air,  than  where  there  is  a  limited  amount  of  fresh 
air  or  none  at  all. 

No.  4.  Timber  of  any  kind  will  last  longer  underground  when  wet,  or 
when  there  is  sufficient  moisture  in  the  ground  or  air  to  keep  it  damp.  Fun- 
gus will  not  form  on  timbers  where  there  is  a  good  circulation  of  pure  air, 
but  forms  rapidly  where  there  is  little  or  no  air. 


TIMBER  USED   IN  MINING  5 

No.  5.  It  is  impossible  to  figure  on  an  average  condition.  We  have 
seen  large  timbers  crushed  into  slivers  within  a  few  days  underground,  and 
again  have  seen  timbers  of  the  same  size  perfectly  sound  after  being  under- 
ground for  forty  years.  Spruce,  yellow  pine,  fir  or  cedar,  in  a  well- ventilated 
damp  mine,  where  there  is  no  excessive  pressure,  should  last  for  fifty  years. 
Sugar  pine,  which  is  the  best  timber  we  have,  is  now  too  valuable  for  mining 
work  in  heavy  ground.  Timber  that  will  best  resist  end-thrust  is  the  most 
serviceable  for  mining  work. 

Mr.  E.  Hampton,  who  at  the  time  these  questions  were  sent 
out  was  superintendent  of  the  Oneida  mine,  near  Jackson,  Ama- 
dor  County,  California,  responded  as  follows: 

The  timbers  used  in  the  Oneida  mine  are  yellow,  bull  and  sugar  pine, 
spruce,  fir  and  cedar  (native  timbers) ;  50  per  cent,  is  bull  pine.  Some  Oregon 
pine  is  also  used.  There  are  only  a  few  places  in  the  mine  where  timber  of 
any  kind  has  a  chance  for  a  natural  life  —  that  is,  to  stand  long  enough  to 
resist  decay;  the  ground  being  very  heavy,  there  is  nothing  left  to  tell  the 
tale,  but  where  conditions  exist  that  make  it  possible  to  determine  the  life 
of  a  timber,  I  find  that  bull  pine  timbers,  20  in.  in  diameter,  put  in  place  in 
a  well-ventilated  dry  drift,  four  years  ago,  are  now  rotten  clear  through, 
without  any  perceptible  fungus  growth.  I  have  observed  that  timber  will 
decay  in  the  Oneida  mine  as  readily  in  still  air  as  in  a  current  of  air;  that 
fungus  forms  on  green  as  well  as  on  dry  timbers,  but  that  it  forms  more  rapidly 
on  dry  timbers,  and  that  green  timbers  last  longer  than  dry  timbers;  that 
moisture  in  abundance,  where  pressure  does  not  exist,  has  a  tendency  to 
increase  the  life  of  timbers  indefinitely  regardless  of  ventilation,  especially 
spruce.  We  cleaned  out  a  drift  in  1903  that  had  been  run  in  1870  and  tim- 
bered with  spruce,  and  found  that  those  timbers  that  were  not  broken  were 
as  solid  as  when  first  cut. 

For  all-round  mining  purposes  I  consider  best:  first,  spruce;  second, 
yellow  pine;  third,  bull  pine,  and,  in  this  order,  sugar  pine,  fir,  and  cedar. 
In  heavy  ground  there  is  but  little  use  for  the  last  three,  but  I  believe  that 
cedar  will  resist  decay  longer  than  any  other  timber.  Redwood  I  know 
nothing  about.  In  February,  1896,  the  Oneida  shaft  was  started  and  tim- 
bered with  12  X  12  in.  Oregon  pine.  In  July,  1904,  it  had  to  be  retimbered 
from  the  collar  to  50  ft.  below.  The  timbers  were  all  rotten;  changes  of 
season  and  of  atmosphere  must  have  been  the  causes,  as  gas  from  the  mine 
workings  below  never  reached  the  timbers  in  the  shaft,  it  being  a  down-cast. 
At  75  ft.  below  the  collar  of  the  shaft  moisture  is  a  fixed  quantity,  and  from 
that  point  downward  there  is  no  sign  of  decay.  Oregon  timber  is  good  all- 
round  timber,  but  not  equal  to  California  spruce.  With  pressure  it  splits 
too  easily.  Perhaps  if  the  dealers  would  send  to  the  mines  the  same  kind 
and  quality  of  timber  that  they  send  to  the  University  for  testing  purposes, 
we  might  change  our  opinion. 

Mr.  Frank  F.  Weber,  assistant  superintendent  of  the  New 
Almaden  quicksilver  mines,  Santa  Clara  County,  California,  in 
response  to  the  questions,  offered  the  following: 


6  TIMBERING  AND  MINING 

During  the  last  few  years  the  timber  used  in  our  main  stopes  and  gang- 
ways has  been  Oregon  pine,  although  in  the  early  history  of  the  mine  redwood 
timbers,  either  hewn  or  sawed,  were  universally  employed,  and  the  old  work- 
ings accessible  afford  good  opportunities  for  observing  the  efficiency  of  this 
kind  of  timber  under  varying  conditions.  At  the  time  of  going  into  the 
mine  the  Oregon  timber  had  been  cut  probably  not  longer  than  three  or 
four  months,  so  that  while  it  can  hardly  be  classed  as  well  seasoned,  it  is 
not  as  green  as  that  used  in  some  localities,  where  timber,  abundant  in  the 
vicinity,  is  cut,  framed,  and  ready  for  use  almost  immediately.  Generally 
speaking,  I  believe  that  the  condition  most  unfavorable  to  the  life  of  any 
mine  timber  is  one  of  warmth  with  an  abundance  of  moisture.  In  stopes 
where  this  condition  is  met  with,  the  effect  on  pine  as  observed  here  is  rapid 
decay,  the  timber  being  attacked  by  fungus,  occasionally,  within  from  four 
to  six  months.  Redwood  under  the  same  condition  does  not  seem  to  be 
attacked  so  readily  by  the  fungus,  and  its  life  is  considerably  prolonged. 

In  making  a  comparison  of  the  relative  enduring  qualities  of  redwood 
and  pine  under  favorable  conditions  —  in  an  unusually  cold  and  damp  tunnel 
—  the  following  facts  were  observed:  10  X  10  in.  redwood  timbers,  put  in 
place  over  thirty-five  years  ago,  while  being  sound  at  the  center,  showed  a 
decided  softening  near  the  surface,  although  they  are  still  serving  their  pur- 
pose satisfactorily.  In  the  stopes  requiring  considerable  timber  to  support 
the  ground,  Oregon  pine  (Douglas  spruce)  has  been  employed,  and  is  found 
to  be  the  most  satisfactory  in  every  way.  Especially  is  this  true  where  the 
square-set  system  is  used,  for  in  taking  weight  this  kind  of  timber  will  stand 
a  surprising  amount  of  buckling  and  twisting  before  absolute  failure.  Red- 
wood, on  the  other  hand,  will  not  support  weight  nearly  as  well.  It  is  brittle, 
will  split  and  give  way  with  little  warning  —  sometimes  so  quickly  that 
repairs  are  often  prevented  —  while  pine  shows  at  what  point  repairs  are 
needed  and  allows  ample  time  in  which  to  do  such  work. 

With  regard  to  the  effect  of  carbon-dioxide  gas  on  timber,  I  do  not  believe 
that  it  has  any  noticeable  effect  one  way  or  another.  It  is  met  with  in  con- 
siderable quantities  in  portions  of  this  mine,  and  any  particular  effect  would 
be  noticed.  On  the  other  hand,  foul  gases  arising  from  a  pile  of  decaying 
timber  will  in  all  probability  cause  a  favorable  condition  for  like  decay  in 
adjacent  timbers.  It  would  be  a  hard  matter  to  give  an  accurate  estimate 
as  to  how  long  a  stick  of  timber  would  endure,  even  under  favorable  condi- 
tions. However,  I  should  judge  that  seasoned  redwood,  in  a  wet  drift  or 
shaft,  such  as  that  heretofore  mentioned,  and  coming  in  contact  with  a  cur- 
rent of  fresh  air,  should  last  for  all  practical  purposes  from  thirty  to  forty 
years;  Oregon  pine,  under  like  conditions,  from  fifteen  to  twenty-five  years. 

In  my  opinion,  the  best  timber  for  all-round  mining  work  is  well  seasoned 
pine  of  the  better  varieties  found  throughout  the  Northwest.  As  a  rule, 
it  is  a  strong,  safe  timber  to  work  with,  and  its  life  is  sufficiently  long  for  all 
practical  purposes.  Wherever  possible,  the  class  of  timber  employed  should 
be  that  which  best  suits  the  conditions  met  with,  and  an  ideal  state  of  affairs 
would  be  to  use  redwood  in  all  shafts  and  main  gangways,  and  timber  the  stopes 
and  drifts  of  lesser  importance  with  pine.  The  price  of  redwood  (which  in  this 
locality,  New  Almaden,  is  nearly  twice  that  of  pine)  often  prohibits  its  use. 


TIMBER  USED   IN  MINING  7 

It  is  evident  from   the  several  opinions  of  the  gentlemen 
quoted  above  that  each  speaks  according  to  his  own  experience, 
all  practically  agreeing  that  for  general  —  in  fact,  for  most  — 
purposes,  spruce  is  best. 

The  statement  of  Mr.  Frank  F.  Weber,  that  carbon-dioxide 
has  no  appreciably  destructive  effect  upon  the  timbering  at  New 
Almaden  is  of  interest,  as  some  portions  of  that  mine  are  noted 
for  the  large  amount  of  this  gas  issuing  from  crevices  in  the 
rocks.  He  recognizes,  however,  that  carbon-dioxide  due  to 
decomposition  of  timbers  in  the  mine  has  a  noticeable  effect  in 
promoting  decay  of  new  timbers  placed  in  the  mine  workings. 
It  has  been  suggested,  in  this  connection,  that  possibly  there 
may  be  an  important  difference  in  these  gases  —  between  that 
emanating  from  the  rocks  and  that  due  to  rotting  of  timber  — 
and  that  possibly  the  latter  may  consist  in  part  at  least  of  hydro- 
carbons. 


CHAPTER  II 

PRESERVATION   OF  TIMBERS 

IN  view  of  the  rapid  deterioration  of  timbers  placed  inmost 
mines,  not  wholly  or  at  all  due  to  heavy  pressure,  engineers  have 
for  years  past  experimented  in  an  effort  to  discover  some  means 
of  lessening  this  rapid  decay  of  timbers,  and  several  methods 
have  been  found  which  preserve  timber  for  a  greater  or  less 
length  of  time.  Among  those  who  have  made  an  exhaustive 
study  of  methods  of  preserving  timber  for  use  in  mines  and 
elsewhere,  are  the  large  railroad  companies,  and  more  particu- 
larly the  Forest  Service  of  the  Government.  Gifford  Pinchot, 
Forester,  has  caused  to  be  issued,  as  Circular  111  of  the  Forest 
Service,  a  pamphlet  entitled  "Prolonging  the  Life  of  Mine  Tim- 
bers," written  by  John  M.  Nelson,  Jr.,  forest  assistant.  From 
this  little  work  the  following  notes  have  been  abstracted: 

"  Peeling  the  Timber.  —  Experiments  have  shown  that  peeled 
timber  is  superior  in  durability  to  unpeeled  timber.  The  space 
between  the  bark  and  the  wood  especially  favors  the  development 
of  wood-destroying  fungi  and  is  a  breeding  place  for  many  forms 
of  insect  life.  When,  after  placement  in  the  mines,  the  bark 
begins  to  flake  off,  the  timber  has  already  begun  to  decay.  The 
cost  of  peeling  timber  before  it  goes  into  the  mine  ranges  from 
20  cents  to  50  cents  per  ton  of  wood,  according  to  local  condi- 
tions and  the  kind  of  timber. 

"  Seasoning  the  Timber.  —  Seasoning  or  drying  gives  mining 
timber  greater  strength  and  durability.  A  stick  of  wet  timber 
has  only  about  one-half  the  strength  of  a  similar  stick  absolutely 
dry.  Though  it  is  not  practicable  for  mining  companies  to  hold 
their  timber  until  it  is  absolutely  air  dry,  peeled  timber  will  dry 
out  sufficiently  in  a  few  months  to  gain  in  both  strength  and 
durability.  From  two  to  four  months  is  necessary  for  proper 
seasoning.  If  a  mining  company  handles  its  own  timber  from 
the  woods  to  the  mines,  the  saving  in  freight  made  possible  by 

8 


PRESERVATION   OF  TIMBERS  9 

peeling  and  seasoning  can  readily  be  estimated.  Labor  is  the 
principal  factor  in  the  cost  of  peeling,  while  the  cost  of  seasoning 
must  be  represented  by  the  loss  of  interest  on  the  capital  invested 
in  the  timber  during  the  seasoning  period.  However,  these 
additional  items  of  expense  are  more  than  offset  by  a  maximum 
reduction  in  freight  of  from  30  to  40  per  cent.,  and  by  the  far 
better  condition  of  the  timber  with  regard  to  both  its  life  at  the 
mines  and  the  readiness  with  which  it  will  take  preservative 
treatment.  The  peeling  of  timber  at  the  mines  has  been  unsatis- 
factory and  expensive,  because  of  the  limited  amount  of  yard 
room  and  the  accumulation  of  bark.  The  following  considerations 
favor  peeling  in  the  woods:  (1)  The  saving  in  the  cost  of  freight 
due  to  peeling  and  seasoning;  (2)  the  saving  of  yard  room  at  the 
mines;  and  (3)  the  prevention  of  fungus  disease  and  insect  attack 
by  early  peeling. 

"  Treating  the  Timber.  —  Peeling  and  seasoning  mine  timber 
unquestionably  increase  its  durability.  However,  in  order  to 
prolong  its  life  to  the  fullest  extent,  a  preservative  treatment  is 
necessary.  Impregnated  wood  resists  decay  because  the  pre- 
servative is  antiseptic  and  excludes  the  moisture  necessary  for 
fungus  growth.  Timber  used  in  the  mines  was  treated  with  a 
variety  of  preservatives  under  several  methods  of  application. 
Both  green  and  seasoned  timbers  were  treated  to  determine 
both  the  relative  value  of  the  treatments  and  the  best  method  of 
handling  preparatory  to  treatment.  If  treated  at  all,  the  timber 
must  be  peeled. 

"  Brush  Treatments.  —  Brush  treatments  with  both  creosote 
and  carbolineum  were  applied  in  two  coats  to  the  Pennsylvania 
and  Southern  pines.  A  large  flat  brush  and  a  kettle  of  the  hot 
preservative  are  all  that  is  required  for  this  treatment.  A  very 
small  amount  of  the  preserving  fluid  suffices,  but  the  cost  of  appli- 
cation in  proportion  to  the  results  obtained  is  considerable. 
For  small  individual  operators  who  can  not  afford  the  cost  of  a 
large  plant,  brush  treatments  are  feasible  and  economical.  The 
disadvantages  of  brush  treatments  are:  (1)  The  difficulty  of 
completely  covering  the  timber  and  filling  all  checks  and  cracks. 
(2)  The  very  slight  penetration  secured.  The  subsequent  check- 
ing or  opening  of  the  timber  may  often  allow  disease  to  pass 
through  the  shallow  exterior  band  into  the  untreated  interior 
wood. 


10  TIMBERING  AND  MINING 

"  Open-tank  Treatments.  —  Pitch  pine  and  loblolly  pine  have 
been  most  successfully  treated  with  both  creosote  (dead  oil  of 
coal  tar)  and  a  six  per  cent,  solution  of  zinc  chloride  by  the  open- 
tank  process. 

"Description  of  Tank.  —  The  experimental  open  tank  was, 
for  the  most  part,  constructed  from  old  material  already  in  the 
possession  of  the  company.  A  section  of  an  old  boiler  34  in.  in 
diameter  and  13  ft.  in  length  was  set  vertically  in  the  ground  to 
a  depth  of  5  ft.  This  tank  had  a  double  bottom,  separated  by  a 
space  of  one  foot.  Between  the  two  bottoms  a  coil  of  1-in.  pipe 
20  ft.  in  length  carrying  a  steam  pressure  of  110  Ibs.  per  square 
inch  furnished  the  heating  surface  necessary  to  give  the  pre- 
servative fluid  a  maximum  temperature  of  240°  F.  This  coil 
was  connected  by  a  1-in.  pipe  to  a  10-in.  steam  main  75  ft.  dis- 
tant. The  timbers,  which  were  placed  vertically  in  the  tank, 
were  immersed  by  attaching  a  circular  weight  to  their  lower 
ends.  The  timbers  were  lowered  into  and  hoisted  from  the 
tank  by  means  of  a  small  hand  derrick  with  a  swinging  arm. 

"  Description  of  the  Treatment.  —  The  open-tank  treatment  as 
given  in  this  experiment  was  briefly  as  follows:  Green,  partially 
seasoned,  and  thoroughly  seasoned  timber  was  lowered  into  the 
tank  and  immersed  in  creosote,  or  in  a  zinc  chloride  or  salt  solu- 
tion, at  a  temperature  of  from  90°  to  120°  F.  The  temperature 
of  the  creosote  was  raised  by  the  coils  to  from  212°  to  220°  F., 
and  that  of  the  zinc  chloride  or  the  salt  solution  to  about  212°  F. 
In  no  case,  however,  was  the  temperature  allowed  to  go  above 
240°  F.,  for  fear  of  injuring  the  fiber  of  the  timber  and  so  decreas- 
ing its  strength.  When  this  hot  bath  was  over  the  steam  was 
turned  off  and  the  timber  was  allowed  to  stand  until  the  liquid 
cooled  to  a  temperature  of  from  170°  to  100°  F.  The  periods  of 
heat  and  of  cooling  were  varied  for  each  kind  of  timber  and  for 
each  stage  of  its  seasoning.  The  time  required  for  the  cooling 
operation,  which  depended  largely  upon  the  temperature  of  the 
atmosphere,  was  usually  from  3  to  12  hours.  For  the  whole 
treatment  the  time  varied  from  6  to  20  hours. 

"  Theory  of  the  Open-tank  Process.  —  The  theory  of  the  open- 
tank  process  may  be  given  in  a  few  words.  The  heat  of  the 
preservative  expands  and  expels  a  portion  of  the  air  and  water 
contained  in  the  cellular  and  intercellular  spaces  of  the  wood 
tissue,  and  as  the  preservative  cools  there  is  a  contraction  and 


PRESERVATION   OF   TIMBERS  11 

condensation  of  the  air  and  water  which  remain.  To  destroy 
the  partial  vacuum  thus  formed,  the  liquid  is  forced  by  atmos- 
pheric pressure  into  the  cellular  and  intercellular  spaces,  a  process 
aided,  of  course,  by  capillary  attraction.  In  point  of  fact,  there- 
fore, the  hot  bath  merely  prepares  the  wood  for  absorbing  the 
preservative,  and  the  actual  impregnation  follows  as  the  pre- 
servative cools.  The  ease  and  effectiveness  with  which  timber 
can  be  treated  by  this  process  depend  upon  the  kind  of  wood 
and  its  degree  of  dryness.  In  one  species  the  structure  of  the 
wood  tissues  may  effectually  resist,  and  in  another  may  greatly 
favor,  the  expulsion  of  air  and  water  during  the  hot  bath;  in 
seasoned  timber  air,  and  in  green  timber  water,  is  the  chief  ele- 
ment to  be  removed  before  the  wood  can  be  impregnated,  and 
since  air  may  be  expelled  much  more  easily  than  water,  seasoned 
timber  is  the  more  successfully  treated. 

"  Possibilities  and  Regulations  of  the  Treatment.  —  Loblolly 
and  pitch  pine,  among  the  more  important  mining  timbers  of 
the  anthracite  region,  have  been  treated  by  the  open-tank  process 
with  particular  success.  By  simply  immersing  the  timber  first 
in  hot  and  then  in  cold  preservative  fluids,  a  penetration  of  from 
1  in.  in  green  timber  to  from  4  to  5  in.  in  seasoned  timber 
has  easily  been  secured.  Aqueous  solutions  of  zinc  chloride  and 
common  salt  have  been  absorbed  with  as  much  ease  as  creosote. 
In  timbers  which  have  a  considerable  proportion  of  heartwood 
the  line  of  demarcation  separating  heartwood  and  sapwood  is 
frequently  also  the  line  separating  the  treated  and  the  untreated 
wood.  In  past  experiments  with  the  open-tank  process,  the 
heartwood  has  not  been  penetrated  to  a  great  depth,  though 
this  may  be  accomplished  hereafter.  The  sapwood  of  chestnut 
and  red  oak  has  been  treated  with  a  fair  degree  of  success,  but 
with  extremely  little  penetration  of  the  heartwood.  With  abso- 
lutely green  timber  it  has  been  a  question  of  obtaining  the  greatest 
possible  impregnation  in  the  entire  period  of  treatment  (20  hours) . 
For  green  timber  the  period  of  heat  or  preparation  for  treatment 
has  been  increased  from  its  usual  length  (7  hours)  to  18  hours, 
and  this  timber  has  been  given  two  separate  entire  treatments 
on  successive  days  without  any  improvement  over  the  standard, 
treatment  of  20  hours.  The  treatment  of  loblolly  and  pitch  pine 
is  regulated  by  the  proportion  of  heartwood  and  sapwood  con- 
tained and  the  degree  of  seasoning  reached.  With  a  stick  of 


12 


TIMBERING  AND  MINING 


pine,  absorption  is  more  easily  controlled  by  varying  the  dura- 
tion of  the  cold  bath  than  by  varying  that  of  the  hot  bath.  The 
duration  of  the  hot  bath  necessary  to  prepare  any  form  or  kind 
of  timber  for  impregnation  is  exceedingly  variable.  Seasoned 
timber,  however,  absorbs  the  cooling  preservative  with  a  fair 
degree  of  regularity  down  to  a  temperature  of  120°  F. 

"  Summary  of  the  Open-tank  Treatment.  —  (a)  Loblolly  and 
pitch  pine  can  be  successfully  and  economically  treated  by  simple 
immersion  in  successive  hot  and  cold  baths  in  an  open  tank  at 


Side  View 

FIG.  1.  —  Plant  for  Treatment  of  Mine  Timbers 


a  cost  of  about  11  cents  per  cubic  foot.  (6)  Green  timber  is 
treated  with  far  more  difficulty  than  seasoned  timber,  (c)  The 
difference  in  weight  of  green  timber  before  and  after  treatment 
is  by  no  means  indicative  of  the  amount  of  the  preservative 
absorbed.  The  simple  application  of  the  hot  liquid  to  green 
timber  slightly  reduces  its  weight  and  yields  no  penetration. 
The  same  application  to  seasoned  timber  slightly  increases  its 
weight  and  gives  a  slight  penetration.  Green  timber  after  treat- 
ment may  show  a  penetration  of  1  in.  without  an  increase  in 
weight,  (d)  Heartwood  of  both  loblolly  pine  and  pitch  pine  is 


PRESERVATION   OF  TIMBERS  13 

penetrated  with  far  more  difficulty  than  is  the  sapwood  of  the 
same  species.  This  is  especially  the  case  with  pitch  pine,  which 
clearly  shows  after  treatment  a  distinct  division  between  the 
treated  sapwood  and  the  untreated  heartwood.  (e)  Experiments 
indicate  that  for  pine  timbers  of  the  same  degree  of  dryness,  or 
containing  equal  proportions  of  heartwood  and  sapwood,  impreg- 
nation can  be  regulated  by  increasing  or  decreasing  the  duration 
of  the  cooling  bath. 

"  Cylinder  Treatment.  —  Loblolly  pine  gangway  timber  was 
treated  for  experimental  purposes  in  a  closed  cylinder  under  pres- 
sure. One  portion  of  this  timber  was  treated  with  12  Ibs.  of 
creosote  per  cubic  foot,  and  the  remainder  with  a  5  or  6  per  cent, 
solution  of  zinc  chloride. 

"  Method  of  Treatment.  —  The  timber  to  be  treated  was  loaded 
on  trucks  and  drawn  into  a  6-ft.  steel  cylinder  by  means  of  a 
wire  cable.  The  doors  of  the  cylinder  were  closed,  and  steam 
was  turned  in  at  the  required  pressure  for  from  4  to  6  hours. 
When  the  steam  had  been  allowed  to  escape  and  the  condensed 
water  in  the  cylinder  to  run  off,  a  vacuum  of  22  in.  was  applied. 
During  this  process  steam  was  passed  through  the  heating  coils 
within  the  cylinder.  The  preservative  fluid  was  then  run  into 
the  cylinder  and  pressure  was  applied  until  the  desired  absorp- 
tion was  attained. 

"  Comparative  Cost  of  Open-tank  and  Cylinder  Treatments.  — 
The  method  of  treatment  in  a  closed  cylinder  under  pressure  is 
effective  but  expensive.  Here,  as  in  the  previous  treatments, 
the  cost  of  the  preservative  is  a  large  item,  but  the  cost  of  appli- 
cation is  far  greater  by  the  cylinder  process  than  by  the  others. 
The  saving  secured  by  the  open-tank  method  is  due  to:  (1)  The 
omission  of  the  steam,  vacuum,  and  pressure  features  of  the 
cylinder  process  and  the  elimination  of  the  expensive  machinery 
necessary  for  those  stages  of  the  treatment.  (2)  The  light  con- 
struction of  the  tank,  allowed  by  the  lack  of  strain  on  the  walls 
(3)  The  small  amount  of  labor  required  in  the  operation  of  an 
open-tank  plant,  due  to  the  simplicity  of  its  construction  and 
method  of  applying  the  preservative.  (4)  The  fact  that  the  cost 
of  construction  and  maintenance  of  an  open-tank  plant  is  less 
than  one-fifth  that  of  a  cylinder  plant  of  equal  capacity. 

"  Results  Derived  from  Experiments.  —  Though  results  so  far 
derived  from  actual  experiments  do  not  cover  all  classes  of  mine 


14  TIMBERING  AND  MINING 

timber  under  all  conditions,  they  show  that  it  will  unquestion- 
ably pay  mining  companies  to  peel  their  round  timber,  to  season 
it  for  a  few  months,  and  to  treat  it  thoroughly  with  some  good 
preservative.  For  pitch  pine  and  loblolly  pine,  the  open-tank 
process  with  creosote  has  proved  an  efficient  and  economical 
method  of  treatment.  The  preservative  value  of  zinc  chloride 
for  mining  purposes  is  yet  to  be  determined.  Gangway  timbers 
treated  with  creosote  by  the  cylinder  process  are  standing  well. 
Because  of  its  cost,  however,  this  form  of  treatment  should  not 
be  considered  unless,  in  comparison  with  the  far  less  expensive 
open-tank  method,  it  gives  universally  better  results.  Timbers 
treated  by  the  brush  method  with  creosote  and  carbolineum  have 
so  far  effectively  resisted  decay.  Because  of  the  very  simple 
method  of  application,  brush  treatment  may  prove  advantageous 
for  small  consumers,  or  where  the  timber  is  in  great  danger  of 
being  broken  by  excessive  crushes. 

"As  a  direct  result  of  these  co-operative  experiments,  the  com- 
pany is  considering  the  advisability  of  treating  their  mine  timber 
on  a  more  extensive  scale.  Plans  have  been  drawn  up  for  the 
construction  and  erection  of  a  commercial  open-tank  wood- 
preserving  plant  at  one  of  its  collieries.  This  plant  will  have  a 
daily  capacity  of  about  thirty  sets  of  gangway  timber  (800  cu.  ft.) 
and  will  be  large  enough  to  treat  all  timber  at  this  colliery  except 
that  which  is  broken  or  worn  out.  Creosote  or  a  solution  of  zinc 
chloride,  or  both,  will  be  the  preservative  fluids  used,  although 
the  plant  is  designed  for  the  use  of  any  preservative  which  may 
prove  efficient. 

"  A  Timber  Policy  for  Preservative  Treatment.  —  If  a  mining 
company  has  proved  by  actual  experiment  that  timber  preserva- 
tion is  practical  and  economical,  it  should  be  in  a  position  to 
carry  it  out.  To  do  this  timber  cannot  be  rushed  directly  from 
the  woods  to  the  mines;  there  must  be  time  for  preparing  it  for 
treatment  and  for  treating  it.  This  means  the  storage  of  a  reserve 
supply  of  felled  timber  at  one  or  more  points.  To  insure  a  regu- 
lar supply  of  timber  for  their  present  and  future  needs,  mining 
companies  should  purchase  and  operate  tracts  of  timber  land. 
For  such  an  investment  to  be  permanent,  the  logging  must  be 
carefully  and  economically  done,  and  the  forest  protected  from 
fire  and  managed  on  sound  principles.  The  timber  should  be 
peeled  immediately  upon  being  felled  in  the  woods,  and  allowed 


PRESERVATION   OF   TIMBERS  15 

to  season  while  waiting  on  cars  for  shipment.  In  this  way  freight 
charges  on  bark  and  a  portion  of  the  water  present  in  green  wood 
will  be  saved  and  the  timber  will  be  rendered  more  resistant  to 
decay.  In  many  cases  the  time  consumed  before  and  during 
transportation  may  be  enough  to  season  the  timber  sufficiently 
to  prepare  it  for  preservative  treatment  on  its  arrival  at  the 
mines.  A  careful  and  thorough  inspection  of  all  timber  is  strongly 
recommended.  It  would  be  poor  economy  to  apply  expensive 
preservative  treatments  to  defective  material.  Timber  cut  from 
land  owned  by  the  mining  company  should  be  inspected  in  the 
woods  or  at  the  point  of  shipment,  to  avoid  unnecessary  freight 
charges.  Timber  shipped  to  the  mines  by  outside  parties  should 
be  just  as  carefully  inspected.  At  present,  timber  is  sometimes 
accepted  in  such  condition  that  it  is  doubtful  whether  its  service 
in  the  mines  would  pay  for  the  cost  of  setting  it,  exclusive  of  the 
cost  of  the  timber.  No  matter  how  critical  the  timber  situation 
may  be,  it  is  believed  that  the  policy  of  accepting  everything  is 
a  poor  one." 


CHAPTER  III 

DRIFTING   AND   DRIFT  SETS 

HAVING  discussed  at  length  the  various  kinds  of  timber  used 
in  Western  metal  mines  generally,  and  the  means  employed  to 
enable  this  timber  to  resist  premature  decay,  we  will  now  take 
up  the  practical  methods  of  timbering  mines,  beginning  with  the 
simplest  forms  of  mine  openings  —  drifts  and  cross-cuts.  While 
it  is  true  that  drifts  and  cross-cuts  are  essentially  the  simplest 
form  of  mine  workings,  the  problem  of  sustaining  the  ground 
through  which  such  excavations  pass  is  not  always  simple,  by 
any  means,  for  in  these  workings  are  encountered  slips,  which 
may  cause  an  unanticipated  fall  of  rock  with  possibly  serious 
and  sometimes  fatal  consequences.  There  are  zones  of  fracture 
to  be  passed  through  wherein  the  ground  may  be  heavy  and 
require  extreme  care  in  handling,  and  in  the  placing  of  timber- 
sets  to  secure  it;  running  ground  is  another  bane  of  the  miner's 
life,  and  this  also  requires  special  methods  and  experienced  men. 
Then  there  is  swelling  ground,  not  so  dangerous,  usually,  as 
either  heavy,  running  or  caving  ground,  but  most  difficult  to 
support  in  such  manner  that  it  can  be  held  without  removal  of 
the  timber  at  frequent  intervals.  Swelling  ground  is  the  most 
expensive  ground,  usually,  that  the  metal  miner  is  required  to 
handle,  and  yet  even  this  can  be  so  managed  as  to  give  the  mini- 
mum of  trouble. 

In  timbering  drifts,  as  in  every  sort  of  mine  workings,  there 
are  certain  underlying  mechanical  principles  which  must  be  ob- 
served if  success  in  preventing  collapse  of  the  workings  is  to  be 
attained.  As  no  two  mines  are  exactly  alike,  and  as  different 
kinds  of  rock  often  require  differing  kinds  of  artificial  support 
when  an  excavation  has  been  made  in  them,  the  miner  must 
necessarily  be  versatile  in  his  timber  schemes,  and  in  the  manner 
of  applying  them.  The  accompanying  sketches  show  some  of 
the  simplest  methods  of  placing  drift  timbers:  Fig.  2  illustrates  a 

16 


DRIFTING  AND   DRIFT  SETS 


17 


method  of  placing  timbers  in  ground  which  stands  fairly  well, 
but  which  may  slack  and  drop  upon  exposure.  The  posts  are 
set  upright;  no  sill  is  provided  beneath  the  posts,  the  ground 
being  firm  and  dry;  but  this  is  a  matter  for  mature  judgment 
for  if  the  rock  on  the  floor  of  the  drift  be  of  such  character  that 
it  is  firm  and  solid  when  dry,  but  becomes  soft  and  crumbling 
if  wet,  sills  should  be  placed,  in  anticipation  of  the  drift  encoun- 
tering water  further  in,  which,  flowing  out  would  wet  and  soften 
the  ground  near  the  mouth  of  the  tunnel  and  cause  the  sets  to 
settle.  All  of  this  may  be  avoided  by  timely  placing  of  the  sills, 
as  shown  in  Fig.  3.  Tracks  may  be  laid  directly  upon  the  sills 
with  ties  intermediately  between  the  sets.  Whether  wet  or  dry, 
drains  should  be  provided  for  the  passage  of  any  water  that  may 


^?  ^^l  ^^i?  Yf/S/sfl  V////*  Yf^^Y^^A  ^($JPft&  K/W£%3 

1                1 

J                  I 

e 


±=B 


Sill 


FIG.  2. 


FIG.  3 


be  subsequently  encountered.  The  drains  should  be  cut  on  both 
sides  of  the  drift  or  beneath  the  center.  The  matter  of  drainage 
is  a  most  variable  one,  some  mines  making  little  or  no  water, 
others  having  far  more  than  their  share  of  it. 

While  the  sketches  given  (Figs.  2,  3  and  4)  show  drift  sets 
placed  in  an  upright  position,  it  is  customary  to  give  the  posts 
an  outward  inclination,  so  that  the  posts  are  farther  apart  at 
the  bottom  than  at  the  top.  This  is  shown  in  Fig.  5.  Upright 
or  square  drift  sets  are  well  enough  suited  to  easy  ground  where 
there  is  no  great  weight  to  support,  and  where  the  ground 
after  being  cut  stands  well  for  several  hours  or  days.  Lagging 
may  then  be  driven  with  little  or  no  trouble,  the  ends  being 
kept  pointed  upward  by  the  use  of  wedge-shaped  blocks.  A  set 
of  lagging  having  thus  been  placed,  those  of  the  next  set  in 


18 


TIMBERING  AND   MINING 


advance  are  inserted  beneath  the  forward  ends  of  those  of  the 
previous  set,  and  driven  ahead  as  the  work  advances.  The 
particular  methods  of  driving  lagging  will  be  fully  described  and 
illustrated  later. 

Fig.  4  shows  a  method  of  framing  a  square  drift  set  which  is 
frequently  seen  in  mines,  but  which  has  absolutely  nothing  to 
recommend  it,  except  that  in  the  event  of  heavy  side  pressure 
the  posts  cannot  easily  be  thrust  inward,  being  prevented  by  the 
deep  shoulder  of  the  cap.  This  style  of  framing  results  in  the 
loss  of  about  half  the  strength  of  the  cap,  and  the  only  thing 
accomplished  by  it  can  be  better  done  in  another  way. 

A  very  simple  drift  set  is  illustrated  in  Fig.  3,  which  may  be 
adapted  either  to  the  upright  posts  or  to  those  spread  as  shown 


FIG.  4 


FIG.  5 


in  Fig.  5.  The  set  consists  of  a  cap  and  two  posts,  neither  of 
which  are  framed,  being  simply  sawed  off  at  a  right  angle,  or  at 
such  angle  as  the  spread  of  the  posts  requires.  To  prevent  the 
posts  from  being  crowded  together,  a  plank  two  or  three  inches 
in  thickness  is  spiked  to  the  under  side  of  the  cap.  This  plank, 
being  exactly  the  length  the  posts  should  be  apart  at  the  top, 
makes  the  sets  uniform,  and  affords  the  necessary  resistance  to 
side  pressure. 

In  Fig.  5  is  shown  a  good  method  of  centering  sets :  it  is  merely 
an  aid  to  the  eye.  Of  course,  sets  may  be  placed  under  the  direc- 
tion of  an  engineer  using  a  transit,  but  this  is  a  refinement  in 
adjustment  usually  dispensed  with  by  miners.  The  set  may 
be  driven  to  either  side  by  means  of  wedges  until  the  plummet 
line  exactly  coincides  with  the  center  mark  on  the  staff,  as  shown. 


DRIFTING  AND   DRIFT  SETS  19 

In  Fig.  4,  in  the  center  of  the  sketch,  is  shown  a  simple  method 
of  framing  the  post  and  cap  in  drifts  sets,  much  in  vogue  in  some 
camps.  It  may  be  described  as  a  sort  of  double  shoulder,  and  is 
designed  on  the  theory  that  by  its  use  neither  cap  nor  post  is 
likely  to  split  under  pressure:  any  scheme  in  timber  framing 
which  will  accomplish  this  is  well  worthy  of  a  trial.  The  "  spiked 
plank"  illustrated  in  Fig.  3  is  one  of  the  best  of  all  the  methods 
employed  to  secure  the  full  strength  of  the  timbers  used. 

Referring  again  to  Fig.  5:  This  is  a  method  of  framing  and 
placing  drift  sets  that  has  no  superior  in  any  kind  of  ground. 
It  is  the  method  of  framing  and  placing  timbers  most  commonly 
employed  on  the  Mother  Lode  of  California,  and  is  successfully 
used  in  the  heaviest  and  worst  swelling  ground  on  the  Lode. 
By  successful  is  meant  relatively  successful  as  compared  with 
other  methods.  No  other  scheme  of  framing  or  placing  of  tim- 
bers in  heavy  ground  is  known  which  affords  better  opportuni- 
ties for  holding  the  ground,  or  lasts  longer  under  the  unusually 
bad  conditions  often  found  there.  All  ground  on  the  Mother 
Lode  of  California  is  not  heavy,  nor  is  it  all  bad.  There  is  some 
very  good  standing  ground  there.  Most  of  the  mines,  for  instance, 
at  Angels  in  Calaveras  County,  are  in  good  ground.  Occasionally, 
serpentine  or  talc  is  encountered,  and  then  trouble  sometimes 
comes  quickly  and  often,  but  on  the  whole  Calaveras  County 
mines  are  not  notoriously  bad;  but  in  Amador,  the  next  county 
to  the  north,  many  of  the  leading  mines  have  ground  which  none 
but  those  familiar  with  it  can  appreciate.  Not  only  is  this  ground 
often  heavy  —  a  thick  gouge-like  mass  of  crushed  slate  with 
stringers  of  quartz  and  calcite,  difficult  to  hold  because  of  the 
dead  weight,  but  often  on  exposure  it  swells,  and  exerts  an  irre- 
sistible pressure  on  the  timbers.  The  heavy  gouges  may  often 
be  cut  and  timbered  without  great  difficulty  when  the  ground  is 
dry,  but  should  it  become  wet,  then  troubles  multiply  and  danger 
increases,  for  the  ground  may  run.  The  method  of  handling 
running  ground  will  be  treated  later. 

In  most  of  the  Mother  Lode  mines  the  workings  are  chiefly 
in  the  vein  itself.  Particularly  is  this  the  case  with  the  workings 
of  the  earlier  years.  In  many  instances  where  a  drift  is  run  on 
the  vein,  whether  on  solid  quartz  or  on  gouge,  the  adjacent  slate, 
which  very  often  forms  at  least  one  wall  and  sometimes  both, 
may  be  solid  and  firm,  dipping  with  the  vein,  or  near  it,  and 


20  TIMBERING  AND  MINING 

showing  no  disposition  when  freshly  broken  to  give  the  least 
trouble.  A  miner  strange  to  the  ground  would  consider  12-in. 
timber  strong  enough  for  work  in  such  material,  but  the  Mother 
Lode  miner  has  learned  by  expensive  experience  that  he  dare  not 
trust  this  seemingly  kindly  ground,  so  he  puts  in  sets,  disposed 
about  as  in  Fig.  5,  giving  the  legs  a  greater  or  less  spread  accord- 
ing to  his  ideas  gained  by  experience.  The  main  members  of 
these  are  24  in.  and  are  not  infrequently  30  in.  or  more  in  diam- 
eter. Until  a  few  years  ago,  the  custom  was  to  place  these  sets 
4  to  5  ft.  apart  (center  to  center)  and  lag  them  with  heavy  spiling, 
top  and  sides,  driven  closely  together.  In  many  instances,  not 
only  was  the  lagging  quickly  bent,  twisted  and  broken,  but 
unless  relieved  the  posts  were  crowded  in  at  the  foot,  or,  being 
unable  to  move  inward,  due  to  rock  obstruction,  they  would 
bend,  split  and  break  —  often  within  two  or  three  weeks  of  the 
time  they  were  first  placed. 

Experience  in  time  taught  the  mine  superintendents  that 
close  lagging  was  not  the  scheme  best  suited  to  the  conditions 
found  on  the  Mother  Lode,  no  matter  what  they  might  be  else- 
where. Gradually  they  learned  that  the  best  results  were 
obtained  when  heavy  posts  and  caps  were  employed,  and  the  lag- 
ging placed  with  considerable  space  between  them,  so  that  the 
swelling  ground  might  crowd  through  the  open  spaces,  and  thus 
in  some  measure  relieve  the  irresistible  pressure.  Later  it  was 
found  to  be  of  still  further  advantage  to  not  only  leave  liberal 
spaces  between  the  lagging,  but  to  employ  men  to  cut  away 
the  soft  ground  through  these  open  spaces  and  to  shovel  the 
accumulation  into  cars  from  time  to  time  and  thus  keep  the 
main  members  in  place.  Keeping  up  swelling  ground  is  always 
expensive,  but  long  experience  has  proved  that  it  is  economy  to 
treat  it  as  here  described  —  employing  men  to  cut  away  and 
relieve  the  ground,  replacing  an  occasional  broken  lagging,  and 
thus  maintaining  the  main  members  of  the  set  in  place. 

In  some  of  the  drift  mines,  as  well  as  quartz  mines,  of  Cali- 
fornia, swelling  ground  is  encountered.  In  the  former  it  is  the 
bed  rock  that  swells.  Where  this  is  the  case,  either  in  a  quartz 
or  a  drift  mine,  the  bottom  of  the  drift  must  be  cut  out  from  time 
to  time  and  the  track  readjusted  to  grade.  The  legs  of  the  timber 
sets  must  be  given  an  unusually  broad  spread — even  greater 
than  is  indicated  in  Fig.  5,  as  this  generally  gives  more  satis- 


DRIFTING  AND   DRIFT  SETS  21 

factory  results  than  where  they  are  more  nearly  upright.  In 
some  instances,  as  at  one  place  in  the  Oneida  mine,  near  Jackson, 
Amador  County,  California,  the  swelling  ground  was  so  trouble- 
some and  such  a  constant  source  of  expense  that  a  drift  was  run 
through  solid  country  rock  of  the  foot-wall,  around  this  piece  of 
bad  ground.  Soon  after  this,  the  old  drift  was  filled  completely 
by  the  material  crowded  in  from  bottom  and  sides.  We  have 
seen  old  workings  in  some  of  the  mines  of  Amador  County  which 
had  been  reopened  by  new  drifts,  where  the  only  sign  that  mining 
had  ever  been  done  there  was  the  old  timbers,  crushed  and  broken, 
that  were  embedded  in  the  soft  gouge-like  material  that  had 
completely  and  compactly  filled  the  old  drift. 

Thus  far  we  have  gone  on  the  supposition  that  the  ground 
through  which  we  have  been  driving  is  fairly  good  standing 
ground,  not  giving  unusual  trouble  in  either  cutting  or  timbering. 
In  fact,  the  work  could  be  carried  far  enough  in  advance  of  timber 
sets  to  admit  of  the  sets  being  placed  in  position  without  extraor- 
dinary precautions.  Often,  however,  conditions  are  not  so  for- 
tunate, and  the  miner  must  be  protected  overhead  and  on  either 
side  as  the  work  advances.  With  proper  arrangements,  even 
under  conditions  such  as  here  anticipated,  the  work  may  advance 
with  perfect  safety  and  with  rapidity.  Loose  ground,  running 
ground,  and  that  which  is  likely  to  spawl  off  and  drop  without 
warning,  like  the  so-called  "nigger  heads"  in  serpentine,  and 
any  other  ground  that  is  in  any  way  dangerous,  may  be  worked 
and  securely  timbered  by  employing  proper  methods.  We  will 
now  consider  the  methods  of  placing  the  timbers,  driving  lagging, 
the  usefulness  of  the  "false  set,"  of  breast  boards,  and  other 
extraordinary  methods  of  timbering  drifts. 

The  methods  of  timbering  drifts  heretofore  described  are  also 
applicable  to  inclines  of  low  slope.  Not  infrequently  miners 
drive  tunnels  on  a  vein  having  a  low  angle  of  dip.  Mine  work- 
ings of  this  character  may  be  safely  timbered  in  the  same  manner 
as  those  run  at  or  near  a  level.  In  these  inclined  tunnels  the 
dip  of  the  vein  sometimes  makes  radical  changes,  becoming 
steeper  or  flatter.  This  does  not  necessitate  any  change  in  the 
style  of  timbering,  unless  the  vein  plunges  down  so  steeply  that 
shaft  sets  are  required,  that  the  foot  wall  may  also  be  sustained. 
In  any  event  the  miner  will  always  bear  in  mind  one  principle 
—  the  posts  must  be  set  perpendicular  to  the  roof  of  the  incline 


22 


TIMBERING   AND   MINING 


(not  vertical).  As  the  angle  of  dip  increases  the  posts  are  set 
forward  at  the  top  at  a  correspondingly  increased  angle  to  meet 
the  downward  pressure  directly.  This  is  somewhat  different 
from  the  method  of  placing  stulls  (which  will  be  dealt* with  later), 
but  the  posts  must  be  set  as  above  explained  in  order  that  the 
pressure  may  be  evenly  distributed,  and  not  permit  the  timbers 
to  "ride"  either  backward  or  forward.  To  still  further  insure 
against  this,  the  timber  sets,  in  all  types  of  drift  and  tunnel, 
either  horizontal  or  inclined,  are  held  in  place  and  kept  from 
moving  in  either  direction  toward  each  other  by  timbers  extend- 
ing from  set  to  set,  and  so  disposed  as  to  catch  both  post  and 
cap  at  the  corners.  These  timbers  are  called  "  sprags  "  in  Ameri- 


FIG.  6 


FIG.  7 


can  practice.  Sprags  are  also  used  in  other  systems  of  timbering, 
which  will  be  described  later.  A  drift,  flat  or  inclined,  timbered 
without  the  sets  being  properly  spragged,  will  collapse  upon  the 
slightest  movement  of  any  set  out  of  the  perpendicular.  And 
if  one  set  goes  down  from  this  cause  it  is  likely  to  so  weaken  others 
adjacent  to  it  that  the  entire  drift  may  be  wrecked  by  the  falling 
down  or  "jack- knifing"  of  sets. 

In  some  ground  it  is  considered  desirable  to  place  sprags 
both  top  and  bottom  of  the  sets  —  always  at  the  top,  and  near 
the  bottom  when  the  footing  of  the  posts  is  considered  insecure. 
If  the  ground  under  the  posts  be  particularly  soft  or  slick  (talc, 
serpentine  or  clay),  it  is  better  to  employ  sills  upon  which  the 
posts  may  rest,  thus  rendering  the  sets  far  more  secure.  Occa- 


DRIFTING   AND   DRIFT  SETS 


.  23 


sionally  a  drift  is  run  on  a  vein  in  which  the  ground  stands  so 
well  that  no  timber  sets  such  as  described  are  necessary  at  all, 
stulls  only  being  put  in  place,  usually  8  to  9  ft.  above  the  floor 
of  the  drift,  upon  which  lagging  may  be  laid,  and  waste  rock 
for  filling  dumped  upon  the  lagging  after  the  ore  has  been  removed. 
(See  Fig.  6.)  In  other  cases  another  means  of  support  is  em- 
ployed, as  where  the  distance  between  walls  is  considered  too 
great  or  the  character  of  the  walls  too  treacherous  to  render 
simple  stulls  sufficiently  secure.  This  idea  is  illustrated  in  Fig.  7. 
Both  of  these  latter  properly  belong  under  the  head  of  methods 
of  stoping,  and  will  be  more  fully  considered  later. 


FIG.  8 


FIG.  9 


Fig.  8  shows  the  relative  positions  of  post,  cap  and  sprag 
in  a  drift  set.  Although  the  timbers  here  represented  are  square, 
round  timbers  may  be  framed  in  precisely  the  same  manner. 
It  will  be  observed  that  the  sprag  is  so  placed  as  to  hold  both 
cap  and  post  in  position.  Some  miners  use  spikes  to  secure 
sprags  in  place,  but  the  use  of  spikes  and  nails  is  not  to  be  recom- 
mended for  this  purpose. 

Fig.  9  illustrates  a  good  method  of  framing  the  sill  so  that 
the  post  sets  squarely  upon  it,  the  foot  of  the  post  requiring  no 
framing  or  bevel  at  all.  It  not  only  permits  the  post  to  have  a 
good  square  footing  on  the  sill,  but  the  inside  shoulder  formed 
by  the  angle  dap  prevents  the  foot  of  the  post  from  being  easily 
crowded  into  the  drift  by  side  pressure. 


24 


TIMBERING  AND  MINING 


Driving  Lagging  in  Drifting 

In  driving  drifts,  cross-cuts  and  adits  it  is  often  imperative 
to  support  the  ground  by  means  of  lagging  driven  ahead  of  the 
workmen,  and  as  close  to  the  face  of  the  advancing  cutting  as 
possible.  In  ground  of  this  sort  it  is  not  infrequently  necessary 
to  support  the  sides  as  well  as  the  top  of  the  working  place. 
Where  the  ground  stands  fairly  well,  the  timbers  may  be  placed 
and  the  lagging  driven  at  the  convenience  of  the  miners,  often 
the  work  of  excavating  being  carried  8  to  10  ft.,  or  even  more, 
in  advance  of  the  last  set  of  timbers.  By  cutting  the  back  of 
the  drift  high,  and  beveling  off  the  upper  edge  of  each  piece  of 


FIG.  10.  —  The  Usual  Drift  Set  with  False  Set 

lagging,  these  —  5  to  8  in.  wide  and  usually  from  2  to  3  in.  thick 
—  are  driven  ahead,  the  forward  ends  being  inserted  beneath 
the  ends  of  the  last  set  driven  to  place.  The  forward  ends  are 
kept  well  upward  by  means  of  blocks,  as  hereafter  explained. 
However,  where  the  ground  will  not  stand  for  an  hour,  or  even  a 
few  minutes,  the  lagging  must  be  driven  forward  inch  by  inch 
as  the  work  of  removing  the  ground  progresses.  When  the 
ground  requires  this  prompt  and  constant  support,  lagging  cannot 
readily  be  driven  in  the  manner  above  described;  then  a  more 
elaborate  scheme  is  adopted  —  that  of  wedge-shaped  blocks  and 
the  "bridge."  The  method  of  advancing  a  drift  by  means  of  the 
bridge  is  indicated  in  Fig.  10.  In  the  forward  end  of  the  drift, 


DRIFTING  AND   DRIFT  SETS  25 

of  which  the  sketch  is  a  vertical  longitudinal  section,  will  be 
seen  a  set  of  timbers  differing  somewhat  from  the  others.  It 
has  no  bridge,  and  the  posts  of  this  set  are  slightly  higher  than 
those  of  the  other  sets.  This  is  called  a  "false  set,"  and  is  a 
most  useful  arrangement  in  advancing  through  unusually  bad 
ground.  When  a  set  has  been  completed,  and  the  work  of  ex- 
cavation is  continued,  the  workmen  are  protected  and  the  drift 
rendered  secure  by  inserting  the  forward  end  of  the  lagging  under 
the  bridge  of  the  last  set  in  place.  The  bridge  B  will  be  seen 
above  each  set,  being  separated  from  the  cap  in  each  set  by  the 
wedge-shaped  block  W.  One  of  the  blocks  is  placed  at  each 
end  of  the  cap,  and  generally  one  in  the  center,  to  prevent  the 
bridge  from  bending  under  the  weight  of  the  ground. 

The  lagging,  having  the  upper  edge  beveled  off,  as  shown  in 
the  sketch,  is  inserted  between  the  bridge  and  the  cap  and  is 
driven  forward  as  the  work  progresses,  the  ends  being  kept  pointed 
well  upward  by  means  of  a  block,  shown  in  the  last  set,  which 
is  retained  in  position  by  the  upward  pressure  of  the  lagging,  it 
being  occasionally  necessary  to  force  it  into  proper  place  by 
means  of  a  few  taps  of  a  hammer.  When  the  lagging  has  been 
driven  ahead  about  2J  ft.  beyond  the  center  of  the  last  set,  the 
pressure  of  the  heavy  ground  may  be  so  great  as  to  threaten  to 
force  the  lagging  down  by  bending  it,  or  even  causing  it  to  break. 
When  this  is  the  case  the  false  set  is  put  in  place,  the  posts  being 
first  set  up  and  temporarily  held  in  position  while  the  cap  is 
placed  on  the  posts  and  the  set  wedged  as  firmly  as  possible  against 
the  sides  of  the  drift.  This  false  set  is  of  such  height  as  to  catch 
the  forward  ends  of  the  half-driven  lagging,  which  may  now  rest 
upon  the  cap  of  the  false  set.  When  the  work  of  excavation  has 
again  been  advanced  to  a  point  sufficiently  far  to  admit  the 
placing  of  another  regular  set,  the  timbers  are  placed  in  position, 
the  miners  working  in  safety  under  the  protection  of  the  top 
lagging,  and  also,  where  necessary,  that  at  the  side.  The  posts 
are  first  set  up,  care  being  taken  to  get  each  post  in  direct  line 
and  to  give  each  post  an  outward  slope  at  the  bottom  correspond- 
ing to  that  of  the  other  posts  of  the  sets,  the  top  being  spaced 
by  the  framing  of  the  timbers,  every  cap  being  framed  exactly 
alike.  The  lining  up  may  be  done  by  sighting  or  by  means  of  a 
plumb  line  suspended  from  a  nail  driven  at  the  center  of  the 
cap,  the  cord  being  made  to  coincide  with  a  center  mark  on  the 


26  TIMBERING  AND   MINING 

graduated  staff,  as  was  shown  in  Fig.  5.  If  the  posts  are  over 
6J  ft.  high,  it  will  be  necessary  to  construct  a  low  platform  on 
the  floor  of  the  drift  to  enable  the  men  to  work  at  the  cap  and 
bridge. 

When  the  posts  and  cap  are  in  position  the  wedge  blocks  and 
bridge  are  placed  on  top  of  the  cap,  the  set  being  made  secure 
by  wedges  driven  at  the  sides  and  top.  The  false  set  may  then 
be  removed  by  knocking  out  the  foot  of  the  posts,  when  the 
lagging  will  settle  firmly  on  the  bridge.  If  necessary,  the  wedge 
blocks  in  the  last  set  may  be  knocked  out  by  driving  lagging 
against  them,  the  gap  otherwise  left  being  thus  filled.  Having 
done  this,  the  sprags  are  put  in  place  and  securely  wedged. 

When  the  ground  is  of  such  character  that  the  false  set  is 
unnecessary,  the  sprags  may  be  put  in  place  before  the  main 
set  is  firmly  wedged,  the  latter  being  allowed  to  "ride"  forward 
just  far  enough  to  permit  the  sprags  to  clear  the  shoulders  of  the 
daps  on  posts  and  cap,  when  the  set  is  hammered  into  an  exactly 
upright  position.  Where  the  false  set  is  employed  it  is  not  always 
safe  to  do  this,  the  sprags  being  secured  by  wedging.  The  driving 
of  side  lagging  is  accomplished  in  exactly  the  same  manner  as 
that  overhead,  whether  the  bridge  be  used  in  the  work  or  not. 
It  should  be  understood  that  the  bridge  becomes  a  permanent 
part  of  the  set  and  is  not  removed.  The  bridge  should  be  not 
less  than  3  in.  thick  and  6  in.  wide,  and  larger  dimensions  are 
frequently  advisable. 

We  have  here  contemplated  the  employment  of  timbers  10 
to  14  in.  in  diameter,  which  are  readily  placed  by  strong,  expe- 
rienced men,  the  only  kind  of  men,  in  fact,  suited  to  work  in 
the  timber  gang.  There  are  mines,  however,  where  the  ground 
is  so  heavy  that  timbers  24  to  30  in.  in  diameter  are  in  use  in 
the  main  gangways,  which  it  is  necessary  to  keep  open  constantly. 
In  these  sets  it  is  not  uncommon  to  see  the  posts  8  ft.  high  and 
the  caps  7  to  9  ft.  long  at  the  top,  the  upper  part  of  the  drift 
at  the  under  side  of  the  cap  being  4  to  5  ft.  wide  inside  the  tim- 
bers. It  is  manifestly  impossible  for  men  to  lift  from  the  floor 
a  cap  of  these  dimensions  —  8  ft.  long  and  30  in.  diameter,  and 
weighing  from  500  to  700  Ibs.,  and,  if  unseasoned  or  wet  timber, 
even  more  —  and  place  it  in  position  on  the  posts.  It  is  necessary, 
therefore,  to  hold  the  posts  in  position  by  spiking  braces  (lag- 
ging) from  the  last  set  to  the  new  posts,  and  also  pieces  crossing 


DRIFTING  AND  DRIFT  SETS  27 

the  drift,  to  keep  the  posts  apart.  A  platform  is  then  constructed 
by  laying  a  floor  of  planks  on  the  braces,  which  are  placed  about 
30  in.  above  the  floor  of  the  drift  (according  to  the  height  of  the 
posts),  upon  which  the  men  may  stand  while  lifting  the  heavy 
caps  into  place  and  putting  the  bridge  and  blocks  in  position. 
Of  necessity  the  platform  must  be  well  constructed  and  of  sound 
material,  as  it  must  sustain  the  weight  of  the  cap  and  that  of  4 
to  6  men  as  well.  The  men  of  an  experienced  timber  gang  work 
together  "like  clock-work,"  systematically,  quickly,  and  with 
few  words,  and  the  heavy  timbers  are  placed,  blocked  and  the 
job  finished  in  remarkably  short  time. 

The  forgoing  description  is  that  of  driving  through  easy 
ground  —  picking  ground,  in  fact,  that  not  only  is  readily  ex- 
cavated, but  which  threatens  to  drop  on  short  notice,  and  which 
does  so,  unless  promptly  supported. 

The  methods  here  suggested  and  described  will,  if  properly 
applied,  be  found  applicable  to  every  such  case,  but  there  are 
times  when  these  simple  methods  have  to  be  supplemented  and 
elaborated  by  other  arrangements,  quite  as  important  to  the 
advancement  of  the  work  as  the  expedients  already  referred  to. 
We  will  now  consider  running  ground. 


CHAPTER    IV 

DRIVING   IN  RUNNING   GROUND 

RUNNING  ground  is  the  most  difficult  of  all  kinds  of  material 
through  which  the  miner  must  at  times  work  his  way.  Not 
only  does  this  sort  of  ground  require  support  after  excavation, 
but  it  must  be  held  in  check  constantly  while  the  work  is  advan- 
cing through  it.  It  is  sufficiently  bad  at  all  times,  but  when  wet 
the  difficulties  and  dangers  are  multiplied  greatly.  Headway 
through  bad  running  ground  can  only  be  made  by  the  employ- 
ment of  close  lagging  on  top  and  sides.  Plank  is  superior  to 
split  lagging  in  this  work,  as  the  plank,  being  sawed,  is  smooth 
and  when  placed  close  together  leaves  no  cracks  or  open  spaces 
through  which  the  fine  loose  dirt  can  sift  and  eventually  open  a 
considerable  hole,  which,  weakening  the  timber  support,  will 
finally  result  in  a  cave  which  may  be  most  serious  in  its  con- 
sequences. It  is  imperative,  therefore,  to  timber  with  extreme 
care  when  passing  through  running  ground,  and  to  lag  the  ground 
so  thoroughly  with  strong  material  that  there  is  no  likelihood 
of  a  run  ever  starting  so  long  as  the  timbering  is  maintained  in 
good  condition. 

There  is  a  disposition  on  the  part  of  miners  who  find  them- 
selves obliged  to  work  their  way  through  wet,  loose  ground,  to 
crowd  the  work  as  rapidly  as  possible  and  to  get  through  the 
bad  place  quickly.  It  may  seem  paradoxical  to  say  so,  but  just 
the  reverse  has  been  determined  by  experience  to  be  advisable. 
If  the  work  be  advanced  more  deliberately,  it  will  be  found  that 
expense  will  be  reduced,  greater  security  afforded,  and  in  the  end 
better  headway  will  have  been  made  than  where  the  effort  to 
hurry  the  work  has  been  made. 

If  the  timbering  is  thoroughly  done,  and  the  wet  ground  is 
removed  by  slower  degrees,  much  of  the  water  will  drain  out  of 
the  ground  in  the  vicinity  of  the  face  of  the  cutting,  and  the 
ground  will  in  consequence  settle  more  firmly  and  be  more  easily 
removed,  with  lessened  danger  of  a  run. 

28 


DRIVING  IN   RUNNING  GROUND  29 

Breast  Boards 

In  the  last  chapter  the  method  of  passing  through  loose 
ground  was  described  and  illustrated.  To  pass  through  running 
ground  practically  the  same  general  scheme  is  adopted,  but  in 
addition  to  what  was  described  there,  the  miner  employs  what  are 
termed  "face  boards,"  also  called  "breast  boards."  The  manner 
of  using  breast  boards  is  illustrated  in  Fig.  11,  taken  from  Bulletin 
No.  2  of  the  California  State  Mining  Bureau,  a  treatise  on  Mine 
Timbering,  by  the  writer  of  these  papers.  It  illustrates  a  specific 
instance,  which  is  better  than  a  more  general  description.  The 
general  scheme  is  that  followed  by  miners  almost  everywhere, 
the  particular  feature  displayed  in  the  figure  being  the  use  of 
the  "foot  blocks"  beneath  the  posts.  This  was  the  method  of 
timbering  employed  by  Richard  Rowlands,  an  expert  mining 
engineer  of  Placerville,  California,  in  driving  a  drift  through 
heavy  running  ground  in  a  mine  in  Sierra  County,  California. 
As  its  employment  there  was  eminently  successful,  it  is  advised 
here  as  applicable  to  any  situation  which  involves  passing  through 
running  ground.  As  will  be  observed  in  the  sketch,  the  posts 
were  not  set  directly  upon  the  ground,  as  is  usual,  but  upon 
wedge-shaped  blocks  which  in  turn  rested  upon  double,  flat 
foot  blocks,  placed,  as  shown,  at  right  angles  to  each  other.  Sills 
are  of  no  advantage  in  swelling  ground,  and  of  little  use  in  run- 
ning ground.  The  foot  blocks,  however,  give  the  posts  a  broad 
and  firm  support,  and  as  the  base  is  always  accessible,  any  en- 
croachment of  the  ground  from  either  side  or  bottom  may  be 
promptly  removed.  The  wedge  blocks  were  intended  to  prevent 
the  posts  from  taking  a  greater  spread,  and  in  this  case  experience 
showed  that  the  idea  was  correct,  as  the  posts  did  not  shift  in  the 
least.  In  cases  where  the  floor  of  the  drift  is  firm  and  does  not 
swell  upon  exposure,  the  foot  blocks  and  wedge  blocks  may  usually 
be  dispensed  with.  It  is  entirely  a  matter  of  judgment. 

By  carefully  studying  the  sketch,  Fig.  11,  it  will  be  noticed 
that  the  lagging  is  driven  both  overhead  and  at  the  sides,  and  that 
the  bridge  is  employed  in  both  places.  Notice  also  the  framing 
at  the  inside  corner  of  post  and  cap  —  the  former  is  framed  with 
a  bevel,  the  latter  at  a  right  angle.  The  idea  was  to  prevent 
slipping,  but  although  ingenious,  in  the  presence  of  heavy  pres- 
sure it  is  probable  that  the  advantage  of  this  style  of  framing,  if 


DRIVING  IN   RUNNING   GROUND 


31 


it  possesses  any,  would  be  slight.  The  system  of  timbering  here 
illustrated  contemplates  the  use  of  the  false  set  while  driving 
and  of  the  placing  of  intermediate  sets  later,  should  the  weight 
of  the  ground  on  the  lagging  and  main  timbers  seem  to  demand 
it.  In  this  connection  it  is  well  to  remark  that  in  repairing 
timbering  of  any  sort  in  mines,  wherever  there  has  been  a  sub- 
sidence and  it  is  required  to  force  the  timbers  back  into  place, 
there  is  no  device  that  will  compare  in  utility  and  effectiveness 
with  a  hydraulic  jack.  It  occupies  small  space,  is  easily  carried 
from  place  to  place,  and  it  has  a  capacity  almost  beyond  belief. 


FIG.  12.  —  The  Use  of  Saddle  Wedges 

Ordinarily,  miners  drive  sagging  caps  and  other  displaced 
timbers  back  into  position  by  the  employment  of  "  saddle  wedges," 
or  wedges  driven  from  opposite  directions  between  the  sagging 
timber  and  a  post  or  other  form  of  prop  placed  beneath  or  oppo- 
site it.  It  is  effective,  but  cannot  be  compared  with  the  hy- 
draulic jack;  nor  even  with  the  ordinary  jack  screw.  Fig.  12 
illustrates  the  use  of  saddle  wedges.  It  should  always  be  remem- 
bered that  a  hydraulic  jack  is  a  most  useful  tool  about  a  mine, 
and  it  is  surprising  how  few  of  these  valuable  devices  are  in  use 
for  the  purposes  here  suggested. 


32  TIMBERING  AND   MINING 

The  employment  of  "face"  or  "head  boards"  is  the  only 
device  in  timbering  in  mines  that  makes  it  possible  to  pass  through 
running  ground.  In  the  instance  here  illustrated  the  timbers 
are  placed  in  exactly  the  same  manner  as  described  in  the  last 
chapter,  but  the  face  boards  and  head  blocks  are  an  addition  to 
the  method  there  described.  Usually,  for  face  boards,  2-in. 
planks  are  sufficiently  heavy,  being  generally  6,  8  and  12  in. 
wide,  for  convenience  in  working,  the  broad  plank  being  placed 
near  the  bottom  of  the  working.  The  head  blocks  are  usually 
of  4-in.  lumber  and  are  6,  8  and  12  in.  wide,  to  correspond  to  the 
width  of  the  face  boards.  They  should  be  sawed  long  enough  to 
give  them  ample  bearing  at  each  end.  Excavation  proceeds  by 
cutting  away  the  ground  from  beneath  and  behind  the  uppermost 
face  board.  Sometimes  this  board  can  be  removed  entirely 
until  sufficient  ground  has  been  taken  out  to  permit  of  it  being 
forced  forward,  but  more  often  it  is  the  better  plan  to  leave  the 
boards  in  place  and  gouge  out  the  loose  ground  as  well  as  possible 
through  the  small  open  space  between  the  uppermost  board  and 
that  next  below.  After  the  upper  board  has  been  advanced 
several  inches,  keeping  the  side  lagging  driven  up  constantly 
and  held  by  wedges,  the  work  of  excavation  will  proceed  more 
rapidly.  The  operation  is  repeated  from  board  to  board,  work- 
ing from  the  top  downward  until  the  bottom  is  reached.  Toward 
the  bottom  it  is  usually  permissible  to  remove  the  boards,  one  at 
a  time,  as  no  great  amount  of  ground  could  run  into  the  face  of 
the  drift,  but  lax  methods  must  be  guarded  against  constantly, 
and  the  work  conducted,  wherever  possible,  under  the  direction 
of  an  experienced  man,  or  disaster  may  come  quickly  and  per- 
haps result  in  a  fatality. 

In  this  manner  the  work  is  carried  forward,  with  the  aid  of 
the  false  set  previously  described,  until  the  full  length  of  the  lag- 
ging has  been  reached,  when  the  posts  and  cap,  with  the  bridges 
and  blocks  of  the  main  set,  are  placed  in  position.  The  forward 
ends  of  the  lagging  then  rest  upon  the  bridges  and  are  flush  with 
the  forward  end  of  the  new  set.  Excavation  is  then  commenced 
from  beneath  and  behind  the  upper  face  board,  and  the  board 
forced  forward  as  fast  as  the  ground  is  removed,  and  the  work 
continued  downward,  as  before,  until  it  becomes  necessary  to 
put  up  the  false  set.  This  done,  proceed  as  before,  and  thus, 
set  by  set,  the  work  advances,  and  if  the  materials  employed  are 


DRIVING   IN   RUNNING   GROUND  33 

sufficiently  strong  and  properly  placed,  there  should  be  few  stop- 
pages, other  than,  perhaps,  to  allow  water  to  drain  out  of  the 
ground  from  time  to  time.  When  passing  through  fissures, 
zones  of  crushed  rock  and  layers  of  granulated  material,  it  is 
well  to  take  precautionary  measures,  as  such  ground  is  always 
more  dangerous  than  that  which  is  solid  and  not  disturbed  by 
fissuring  or  brecciation. 


CHAPTER  V 

STRUCTURAL  STEEL  IN   MINE   WORKINGS 

BEFORE  proceeding  further  with  the  methods  of  timbering 
drifts,  gangways  and  cross-cuts,  it  will  be  well  to  give  some 
consideration  to  the  increasing  use  of  structural  steel  in  mine 
workings  in  this  country.  Steel  has  long  been  employed  in 
underground  workings  in  Europe,  where  such  use  has  proved 
the  adaptability  of  this  method  of  support  to  the  conditions 
there  found.  The  first  steel  manufacturing  company  in  the 
United  States  to  make  a  feature  of  steel  mine  supports  is  the 
Carnegie  Steel  Company,  of  Pittsburg,  Pennsylvania.  This  com- 
pany has  issued  a  neat  little  pamphlet  on  the  subject,  illustrating 
and  describing  "steel  timbers"  and  their  use.  Two  of  the  most 
important  of  the  sketches  are  reproduced  here,  illustrating  the 
methods  of  joining  the  several  members  of  a  set.  These  members 
are  made  of  a  combination  of  I-beams  and  double  channels, 
placed  back  to  back.  The  steel  beams  here  described  seem  to 
have  thus  far  given  satisfaction,  and  the  probability  is  that  if 
steel  comes  into  common  use  in  the  mines  of  the  West,  a  system 
will  be  evolved  which  will  suit  it  to  all  of  the  varied  requirements 
of  mine  timbering.  The  Carnegie  Steel  Company  thus  describes 
its  "steel  mine  timbers"  and  their  employment: 

"The  use  of  steel  in  mines  for  square  timbers  and  mine  props  as  well 
is  not  an  experiment.  Numerous  installations  have  been  made  in  tubular 
form  in  the  most  important  mines  of  Germany,  while  ordinary  structural 
material,  whether  straight  or  bent,  has  had  large  place  in  the  mining  opera- 
tions of  England  and  France.  The  first  use  of  steel  in  the  mines  in  the  United 
States  seems  to  have  been  made  by  the  Susquehanna  Coal  Company,  under 
the  supervision  of  R.  V.  Norris,  Consulting  Engineer,  and  there  is  in  use 
to-day  in  the  anthracite  region  steel  timbers  which  have  been  in  use  for  twelve 
to  fifteen  years  in  the  deep  parts  of  the  mines,  exposed  to  constant  contact 
with  mine  water  and  without  signs  of  failure  or  corrosion.  Nothing  whatever 
has  been  done  to  protect  the  steel  beyond  painting  it  with  good  heavy  coats 
of  paint,  and  it  is  safe  to  estimate  that  there  are  now  in  use  three  to  four 
miles  of  gangways  timbered  with  steel.  Of  course,  the  use  of  steel  outside 
the  mines  in  the  shape  of  head  frames,  breakers,  etc.,  is  governed  by  the 

34 


STRUCTURAL   STEEL   IN   MINE   WORKINGS 


35 


Steel  Gangway  Support,  Style  A 

Pin  Bearing,  I  Beam  Girder,   Double    Channel   Struts,    Cast  Iron  Base 


Cast   Iron   Filler 


Pin  and  cotter 


Wedges 


Extra,  holes  permit  adjustment 
for  variation  of  size  of  gangway 


Detail  of  connection  of  Girder  and  Strut 


Ubl 


Cast  Iron  Base 


Eye  bolt  cast  in  center- 11/2  Eye 
Cast  Iron  Shoe 


FIG.  13 


36  TIMBERING  AND   MINING 

same  conditions  as  are  met  in  other  structures  above  ground,  and  it  is  con- 
fidently believed  that  its  use  inside  the  mines  will  satisfactorily  meet  all 
conditions  that  may  arise. 

"Beyond  its  long  life,  steel  possesses  other  advantages  as  compared  to 
wood.  It  can  be  cut  to  length  and  fashioned  in  convenient  units  ready  for 
erection,  and  its  smaller  weight  lends  itself  to  convenience  and  economy 
in  erection.  As  is  well  known,  enormous  destruction  of  life  and  property 
has  followed  the  ignition  of  dry  mine  timber  by  the  miner's  naked  lamp. 
It  is  conservatively  estimated  that  the  annual  mortality  in  the  anthracite 
region  due  to  fires  and  accidents  is  in  the  neighborhood  of  one  fifth  of  one 
per  cent  of  the  total  number  of  persons  employed.  In  contrast  thereto, 
steel  is  perfectly  fireproof  and  its  installation  at  the  foot  of  shafts  and  slopes, 
in  pump-houses  and  other  points  liable  to  fire,  will  obviate  to  a  large  extent 
this  destruction  of  life  and  property. 

"When  the  mine  operations  in  any  particular  locality  are  completed, 
it  is  not  worth  the  trouble  and  expense  involved  to  remove  the  timber  that 
has  been  installed  and  it  is  usually  left  in  the  mine  at  a  dead  loss.  In  the 
forms  of  construction  here  recommended,  steel  can  easily  be  removed  and 
repeatedly  re-used,  and  if  by  reason  of  excessive  or  unexpected  stresses  it 
becomes  crippled,  it  still  possesses  a  high  salvage  value  considered  as  scrap 
alone.  There  seems  to  be  no  means  at  hand  by  which  the  actual  load  on  the 
square  timber  used  in  the  gangways  and  props  can  be  ascertained,  and  in 
the  substitution  of  steel  for  wood  under  present  conditions,  it  seems  that  the 
only  method  by  which  to  determine  the  proper  sizes  for  steel  timbers  is  to 
proportion  them  in  accordance  with  the  relative  theoretical  values  of  the 
two  classes  of  material.  In  order  to  arrive  at  the  proper  size  of  steel  timbers 
to  be  used,  it  will  be  necessary  to  ascertain  from  published  tables  the  strength 
of  the  wooden  timbers  ordinarily  used  for  that  purpose,  and  when  this  is 
done,  to  pick  out  from  the  tables  for  steel  those  members  having  a  correspond- 
ing strength.  By  experiment  in  this  direction,  it  will  be  possible  in  the  course 
of  time  to  arrive  at  some  formulas  by  which  the  size  of  steel  timbers  necessary 
for  use  can  be  immediately  obtained  without  this  comparison;  but  for 
the  present,  it  will  be  more  convenient  for  mine  superintendents  who  are 
familiar  with  wood  to  work  from  their  previous  experience  in  this  class  of  con- 
struction and  to  order  accordingly. 

"The  general  arrangement  marked,  'Style  A'  [see  Fig.  13]  shows  that 
form  of  construction  which  was  designated  by  R.  V.  Norris  and  which  has 
been  used  extensively  in  the  anthracite  regions,  consisting  of  a  single  beam 
collar  and  double-channel  legs,  the  legs  being  connected  to  the  beam 
pins,  wedges  and  cast-iron  separators,  and  resting  at  the  bases  on  cast-iron 
pedestals.  This  form  of  construction  has  several  features  to  commend  it. 
It  is  quickly  erected  and  as  quickly  taken  down.  The  general  arrangements 
marked  'Style  C'  [see  Fig.  14]  represent  the  same  general  forms  of  construc- 
tion, which  however,  are  simpler  of  manufacture,  and  therefore  possess  a 
larger  measure  of  economy  in  the  first  cost,  'Style  C'  being  based  on  the  use 
of  special  forms  of  rolled  material  designed  particularly  with  a  view  to  in- 
creased strength  with  less  weight.  Any  of  these  forms  it  is  believed  should 
be  acceptable  for  the  purpose  intended." 


STRUCTURAL  STEEL   IN   MINE   WORKINGS 


37 


Steel  Gangway  Support,  Style  C 

H  Sections    Girder  and  Struts,  Cast   Iron  Cap,  Steel  Baso 


Detail  of  connection  of  Girder  and  Strut 


* 
f 

i 


Cast  Iron  Cap 


Base  Plate 


FIG.  14 


CHAPTER  VI 

TIMBERING   DRIFT   GRAVEL   MINES    IN   CALIFORNIA. 

Breasting  Posts  and  Caps 

IN  California,  the  mining  of  the  auriferous  gravels  of  the 
ancient  rivers  by  what  is  known  as  "  drifting  "  has  become  a  large 
and  important  industry.  These  differ  from  ordinary  gulch 
placers  in  several  respects.  They  are  beds  of  rivers  that  existed 
in  late  Tertiary  times,  and  flowed  as  modern  streams  do  to-day, 
in  channels,  either  in  narrow  gulches,  in  broad,  timbered  valleys, 
or  in  courses  intermediate  between  these  two  extreme  types  — 
though  of  one  thing  we  may  be  assured,  the  ancient  rivers,  for 
most  part,  were  larger  than  the  rivers  in  California  to-day,  and 
the  grades  were  usually  much  flatter.  These  channels  are  often 
found  firmly  cemented  and  generally  covered  by  a  deep  deposit 
of  volcanic  material,  and  are  often  difficult  to  mine.  In  the 
early  history  of  mining  in  California,  these  ancient  channels 
were  recognized  as  such,  but  there  seems  to  have  been  an  impres- 
sion that  they  had  all  formed  one  great  river,  named  by  those 
early  miners  the  "Deep  Blue  Lead."  At  first  these  channels 
were  mostly  worked  by  hydraulic  method,  and  millions  of  cubic 
yards  of  gravel  were  torn  down  by  the  "giants."  Some  of  these 
channels  were  of  prodigious  size  —  great  rivers  one-third  to  half 
a  mile  in  width,  and  even  more,  though  many  of  them  resembled 
in  a  great  degree,  as  to  width  and  grade,  the  gulches  of  to-day. 
The  vast  amount  of  detritus  washed  down  by  the  hydraulic 
miners,  together  with  the  still  larger  amount  of  silt  washed  by 
the  rains  from  the  cultivated  fields  of  mountain  farms,  caused 
considerable  damage  to  agricultural  lands  along  the  streams  in 
the  great  valleys  of  the  Sacramento  and  San  Joaquin  rivers. 
Injunction  suits  brought  by  the  farmers  resulted  in  the  inhibition 
of  hydraulic  mining,  and  over  $100,000,000  invested  in  hydraulic 
mines,  canals  and  other  plants  became  practically  valueless. 

The  miners  then  sought  some  other  method  of  recovering 
gold  from  these  ancient  rivers.  A  few  mines  had  been  worked 

38 


TIMBERING   DRIFT  GRAVEL   MINES   IN   CALIFORNIA       39 

by  tunneling  the  gravel  on  bed  rock.     This  method  of  mining 
now  was  quite  generally  introduced  and  the  methods  improved, 


FIG.  15 

until  drift  mining  became  a  large  and  in  many  cases  a  very  profit- 
able industry.  Often  the  gravel  could  be  attacked  where  the 
end  of  the  channel  had  been  exposed  by  erosion,  or  had  been 


40  TIMBERING  AND  MINING 

cut  by  the  powerful  streams  from  the  giants,  but  in  a  great  many 
instances  the  ancient  rivers  lie  buried  deeply  beneath  the  lava 
cap,  and  often  below  the  drainage  of  the  streams  of  the  vicinity. 
This  latter  fact  often  necessitated  the  driving  of  lengthy  tunnels 
through  the  "rim  rock,"  as  the  bed  rock  of  the  channel  is  called, 
in  order  to  reach  the  channel  proper.  Some  of  these  tunnels  are 
several  thousand  feet  in  length.  The  mining  practice  in  driving 
these  long  cross-cut  tunnels  is  that  generally  pursued  in  tunnel- 
ing or  drifting  in  quartz  mines.  The  same  variations  are  en- 
countered in  tunnels  run  to  develop  drift  mines  as  in  those  driven 
for  water  or  for  the  exploitation  of  quartz  mines.  It  is  with  the 
mining  of  the  gravel  itself  that  the  present  chapter  deals.  In 
order  to  make  the  methods  more  clear,  the  accompanying  sketches, 
Figs.  15  and  16,  have  been  introduced,  taken  from  Bulletin  No.  2 
of  the  State  Mining  Bureau  of  California  —  "  Methods  of  Mine 
Timbering."  Running  ground  is  occasionally  met  in  drift- 
mining  practice,  but  far  more  often  it  is  swelling  bed  rock  that 
gives  the  most  trouble.  This  phase  of  mining  has  already  been 
dealt  with  at  length,  and  need  not  here  be  repeated. 

In  opening  a  drift  mine  it  is  customary  in  the  best  practice  to 
cut  the  main  gangway  (or  more  than  one  in  a  very  wide  gravel 
channel)  to  some  extent  in  the  bed  rock.  This  is  done  for  two 
purposes:  first,  it  aids  in  equalizing  the  inequalities  of  the  bed 
rock,  which  is  usually  found  to  undulate,  more  or  less;  second, 
it  makes  the  loading  of  cars  from  the  platforms  more  easy  and 
consequently  less  expensive.  The  method  of  driving  these  gang- 
ways varies  with  the  character  of  the  ground.  If  necessary,  the 
posts  and  caps  are  employed;  also  lagging,  if  required.  Fig.  16 
represents  a  gangway  driven  partly  in  bed  rock  and  partly  in 
gravel.  This  method  may  be  employed  where  the  ground  is 
fairly  good,  but  where  it  becomes  loose  and  requires  more  care, 
then  the  method  illustrated  in  Fig.  15  should  be  employed.  The 
breast  —  that  is,  the  gravel  bed  on  either  side  of  the  gangway  — 
is  usually  timbered  with  what  the  drift  miners  call  "post  and 
breasting  caps."  These  are  single  posts  with  a  strip  of  heavy 
plank  or  split  lagging  placed  between  the  top  of  the  post  and  the 
roof  of  gravel  or  other  rock.  This  is  made  tight  by  driving 
wedges  between  the  cap  and  the  roof.  The  general  manner  of 
breasting  gravel  is  something  like  the  methods  employed  in  coal 
mines.  As  the  work  of  breasting  proceeds,  the  cobbles  and 


TIMBERING   DRIFT  GRAVEL  MINES   IN   CALIFORNIA       41 


boulders  are  stacked  behind  the  miners,  these  in  time  forming 
a  broad  and  firm  support  to  the  roof.  Often,  where  no  regular 
sets  are  required  in  the  gangways,  walls  are  built  of  the  boulders 
and  cobbles  lining  the  gangways.  Some  mines  do  not  even 


FIG.  16 

require  the  breasting  caps  and  posts,  the  "gob"  or  boulders  of 
the  fill  affording  all  the  support  that  is  necessary.  Some  ground, 
on  the  other  hand,  requires  a  comparatively  elaborate  system  of 
timbering.  The  two  principal  methods  employed  are  depicted  in 
Figs.  15  and  16. 


CHAPTER  VII 

SHAFTS 

Location,  Kind  and  Size  of  Shafts.     Substantial  Timbering  Usually 

Necessary 

SHAFTS  generally  require  more  careful  planning  than  almost 
any  other  kind  of  mine  work.  The  first  thing  to  be  considered 
is  the  location  of  the  shaft.  In  most  instances  the  shaft  is  not  a 
matter  of  careful  consideration  with  the  miner,  particularly  with 
the  prospector,  who  begins  to  sink  where  he  finds  good  ore  at  the 
surface,  or  at  a  point  where  he  anticipates  striking  ore  within 
a  short  distance  of  the  surface.  He  gives  little  thought  to  engi- 
neering features,  or  to  economical  considerations,  other  than  to 
put  the  shaft  down  as  quickly  and  as  economically  as  possible 
with  the  means  at  command.  The  result  is  that  a  prospect 
shaft  is  seldom  useful  as  a  working  shaft,  though  not  infrequently 
a  shaft  suitable  for  a  working  shaft  of  large  capacity  is  sunk  to 
prospect  a  vein  or  ore  deposit  —  a  bad  practice  and  one  not  to 
be  recommended  on  undeveloped  property,  unless  the  probabili- 
ties have  been  already  demonstrated  in  an  adjoining  mine. 

Prospectors  are  fully  justified  in  sinking  small  shafts,  and  it 
is  a  good  general  rule  to  sink  prospect  shafts  on  the  vein  when- 
ever possible.  There  are  few  exceptions  where  conditions  justify 
a  departure  from  this  excellent  rule.  Not  infrequently,  however, 
large  and  usually  well-appointed  shafts,  thoroughly  equipped 
with  hoisting  plant  and  other  essentials  of  a  large  operation, 
may  be  seen  being  sunk  on  the  merest  prospect  —  little  or  no  ore 
in  sight  to  justify  more  than  an  ordinary  prospect  hole.  It  is 
needless  to  say  that  these  enterprises  are  the  outcome  of  some 
elaborate  promotion  scheme,  the  chief  function  of  which  evi- 
dently is  to  enrich  the  promoters,  regardless  of  the  intrinsic  value 
of  the  property  or  its  prospective  worth.  Nevertheless,  such 
shafts  are  often  models  of  engineering  excellence. 

Prospectors  are  frequently  excellent  miners,  from  the  stand- 
point of  economy.  They  can  put  down  a  shaft  and  support  the 

42 


SHAFTS  43 

loose  and  threatening  rocks  in  a  most  ingenious  manner.  Most 
experienced  mining  engineers  who  step  upon  the  platform  of  a 
cage  or  skip  over  a  hole  2000  to  5000  ft.  deep  without  the  slightest 
fear,  look  down  into  the  dark  depths  of  a  prospect  hole  less  than 
100  ft.  deep  with  apprehension,  and  descend  in  the  bucket  or 
upon  the  rickety  ladders  with  many  misgivings.  This  is  only 
natural.  In  the  former  there  is  every  evidence  of  substantial 
materials,  superior  workmanship  and  engineering  skill;  in  the 
latter  on  every  hand  may  be  seen  the  makeshift,  the  apparently 
insecure,  and  an  absolute  lack  of  knowledge  of  anything  like 
engineering  practice,  though  a  more  careful  scrutiny  will  usually 
prove  that  skill  has  not  been  lacking.  There  are  no  extra  or 
unnecessary  timbers.  Every  loose  block  is  firmly  supported, 
and  the  ladders,  though  not  models  of  neatness,  are  usually 
strong  enough  for  the  purpose  for  which  they  are  intended. 
Prospect  shafts  should  be  sunk  on  the  vein  or  in  the  ore  deposit. 
Good  prospects  have  not  infrequently  been  lost  to  the  original 
owners  by  failure  to  follow  the  vein.  A  large  amount  of  work 
may  be  done  in  a  shaft  off  the  vein;  funds  becoming  exhausted 
and  no  paying  ore  developed,  the  miner  quits,  and  another  later 
develops  a  mine  by  staying  with  the  ore. 

A  shaft  intended  for  working  purposes  can  only  be  intelli- 
gently located  after  the  mine  has  been  sufficiently  developed  to 
determine  the  position  and  extent  of  the  ore.  Not  only  must 
the  position  of  the  ore  bodies  be  known,  but  their  trend  as  well, 
and  if  there  are  two  or  more  veins  in  proximity  the  shaft  should 
be  located  with  due  reference  to  the  several  veins.  The  topo- 
graphical situation  is  also  important.  When  ore  has  been  hoisted 
to  the  surface  it  must  be  disposed  of  —  sent  to  mill  or  smelter, 
to  railroad  cars  or  to  wagons,  to  be  transported  to  some  place 
more  or  less  distant.  Roads  must  often  be  considered;  conse- 
quently the  shaft  must  be  started  at  a  point  readily  accessible 
by  heavily  laden  teams,  both  for  the  quick  and  economical  hand- 
ling of  machinery,  timbers  and  other  supplies,  and  for  the  hauling 
away  of  ore  and  waste  rock.  Particularly  is  it  desirable  to  have 
the  shaft  at  a  place  which  will  afford  transportation  of  ore  by 
gravity  to  the  reduction  works.  Where  possible,  there  should 
be  sufficient  fall  between  them  to  admit  of  the  placing  of  a  large 
ore  bin,  below  which  should  be  situated  the  rock  breaker,  dis- 
charging into  a  second  bin,  from  which  the  ore  may  be  drawn 


44  TIMBERING  AND  MINING 

and  sent  directly  to  the  mill  or  smelter,  if  on  the  property,  by 
gravity.  This  very  important  desideratum  in  the  economy  of 
mining  is  too  often  overlooked  or  neglected  as  of  minor  importance. 
If  a  large  tonnage  is  to  be  handled,  it  may  mean  a  vast  difference 
in  cost.  Assume  a  mine  which  will  produce  1,000,000  tons  of 
ore.  The  additional  unnecessary  expense  of  five  cents  per  ton 
in  elevating  the  ore  to  the  mill  after  it  has  been  raised  to  the 
collar  of  the  shaft,  when  it  may  have  been  avoided  by  locating 
the  shaft  at  some  higher  point,  means  an  outlay  of  $50,000, 
which  would  in  most  cases  far  more  than  offset  the  possible 
additional  cost  of  sinking  the  shaft  at  some  other  place.  The 
illustration,  Fig.  17,  shows  a  shaft  located  with  reference  to 
metallurgical  operations. 

Another  thing  to  be  avoided  is  the  sinking  of  a  shaft  in  a 
gulch  at  a  level  so  low  that  there  is  even  a  slight  possibility  of  a 
freshet  pouring  down  the  shaft,  flooding  the  mine  and  possibly 
causing  the  death  of  men  working  below.  This  caution  is  the 
result  of  knowledge  of  several  shafts  so  located  that  this  mis- 
fortune actually  occurred.  In  some  instances  shafts  are  sunk 
on  the  side  hill  sufficiently  high  to  be  above  high-water  mark, 
but  where  much  surface  drainage  finds  its  way  through  the  soil 
and  loose  rocks  into  the  shaft.  This  may  be  largely,  if  not  wholly 
eliminated,  by  building  a  substantial  wall  of  concrete  about  the 
shaft,  this  wall  having  a  base  far  enough  below  the  surface  to  cut 
off  any  such  superficial  drainage.  Concrete  is  also  advisable 
around  the  collar  of  a  shaft  sunk  through  loose  ground  where  the 
shaft  is  not  situated  in  a  gulch.  There  is  an  increasing  tendency 
to  employ  concrete  in  many  places  underground,  its  usefulness 
and  economy  being  constantly  demonstrated. 

No  branch  of  mining  practice  has  received  more  careful 
attention  than  shaft  sinking.  It  is  the  most  important  phase  of 
all  mining  work.  Large  working  shafts  are  necessarily  expen- 
sive, and  they  should  be  so  made  and  equipped  that  they  can  be 
kept  open  as  long  as  there  remains  ore  in  the  mine  that  may  be 
extracted  at  a  profit.  Engineers  have  devoted  much  time  to 
devising  methods  of  shaft  sinking,  with  a  view  to  improving 
practice  while  hastening  the  speed  with  which  the  work  is  accom- 
plished. In  many  cases  the  desired  result  has  been  attained, 
but  as  a  rule  the  expense  has  not  been  decreased  correspondingly. 
However,  there  is  one  feature  in  the  economy  of  shaft  sinking  too 


SHAFTS 


45 


46  TIMBERING  AND   MINING 

often  lost  sight  of,  and  that  is  the  necessity  for  as  great  speed 
as  possible  commensurate  with  good  workmanship  and  safety. 
Where  large  capital  is  invested  in  a  mining  operation,  the  in- 
terest charge  is  an  item  of  no  small  consequence,  and  speed  in 
shaft  sinking  often  justifies  an  increase  in  expense  per  foot. 
This  has  given  rise  to  the  premium  system  so  successfully  applied 
in  sinking  the  deep  shafts  on  the  Rand  in  South  Africa.  The 
spur  of  additional  pay  for  additional  work  is  seldom  without  the 
desired  effect  on  the  miner,  be  he  American,  Cornishman,  Mexi- 
can, Kaffir,  Chinaman,  or  any  other.  It  is  an  excellent  system 
when  wisely  applied. 

Prospecting  Shafts   in  Good   Ground  and   Those  Requiring  Close 
Timbering.     Cribs  and  Single-Compartment  Shafts 

Prospectors  often  sink  shafts  to  surprising  depths  by  means 
of  hand  windlass  or  horse  whim,  employing  little  or  no  timber. 
Of  course  this  is  only  possible  where  the  ground  stands  well. 
Near  the  village  of  Mokelumne  Hill,  in  Calaveras  County,  Cali- 
fornia, are  shafts  sunk  in  1851-52,  to  a  depth  of  350  ft.  or  more, 
which  have  no  timber  from  top  to  bottom  and  never  had.  The 
rock  was  hoisted  by  means  of  windlasses,  and  although  these 
shafts  were  sunk  nearly  sixty  years  ago,  they  are  as  good  and  safe 
to-day  as  when  they  were  put  down.  This  is  due  to  the  fact 
that  they  were  sunk  in  the  volcanic  tuff  that  overlies  an  ancient 
river  channel.  These  holes  are  circular,  about  four  feet  in  diam- 
eter, and  vertical.  In  the  Calico  mining  district,  San  Bernardino 
County,  California,  are  shafts  200  ft.  and  more  in  depth  that  are 
without  timbers,  having  been  sunk  in  the  early  eighties.  These 
shafts  are  in  the  rhyolite  tuff  of  that  region,  and  as  the  climate 
there  is  remarkably  dry,  they  are  open  and  in  good  condition 
to-day,  although  they  are  rectangular  or  square  in  section. 
Doubtless,  shafts  may  be  and  have  been  safely  sunk  under  similar 
conditions  in  many  other  places,  but  ordinarily  it  is  not  only 
wise,  but  necessary,  to  use  timber  in  shaft  sinking  in  most  rocks 
(tuffs  being  about  the  only  exception),  and  even  in  this  kind  of 
ground  it  would  be  unsafe  to  use  such  shafts  for  working  purposes 
without  the  employment  of  some  timber. 

In  other  places  in  the  desert  regions  of  California,  Nevada  and 
Arizona,  prospectors  have  sunk  shafts  several  hundred  feet  in 
depth,  both  vertical  and  inclined,  where  only  the  timber  abso- 


SHAFTS  47 

lately  necessary  was  put  in  —  each  stick  being  placed  to  support 
some  particular  block  or  mass  of  rock.  As  these  several  rock 
masses  require  support  from  various  directions,  the  timbers  are 
placed  like  stulls  in  a  stope  and  exhibit  no  regularity  of  distribu- 
tion. Often  the  appearance  of  these  shaft  stulls  reminds  one, 
looking  upon  them  from  above,  of  a  corkscrew.  Where  the  shaft 
remains  constantly  dry,  and  the  timbers  have  been  properly 
placed  and  well  wedged  when  put  in,  there  is  comparatively  little 
danger,  but  where  there  are  alterations  of  wet  and  dry,  there 
arises  a  great  danger,  unless  the  miners  frequently  inspect  the 
timbering  and  keep  the  wedges  well  driven.  The  reason  for 
this  is,  that  when  wet  the  wedges  swell,  and  all  is  secure,  but  when 
the  atmosphere  becomes  dry  the  wedges  shrink,  and  if  the  neces- 
sary attention  is  not  given  them  the  timbers  are  more  than  likely 
to  drop  out  of  their  own  weight,  unless  the  rocks  settle  more 
firmly  upon  them,  which  immediately  creates  a  new  danger  in 
the  threatened  caving  of  the  ground.  All  this,  however,  can  be 
largely,  if  not  wholly,  avoided  by  keeping  the  wedges  tightly 
driven  at  all  times.  Prospectors  will  generally  utilize  such  timber 
as  is  most  readily  and  cheaply  obtainable.  On  the  desert,  long 
experience  has  demonstrated  that  almost  any  kind  of  timber 
support  will  do,  and  consequently  in  the  prospect  holes  of  the 
great  Southwest  may  be  seen  old  railroad  ties,  knotty  sticks  of 
juniper,  scrub  pines,  scantling,  and  even  yuccas  and  sage  brush 
-the  latter  in  place  of  lagging  —  to  hold  back  small  rocks. 
In  the  timbered  regions,  the  prospector  is  more  painstaking,  for 
several  reasons.  In  the  first  place,  there  are  in  such  regions 
alternating  seasons  of  wet  and  dry,  and  his  ground  requires 
more  elaborate  support;  then  he  has  usually  an  assortment  of 
timber  from  which  to  choose,  both  as  to  kind  and  size,  but  he 
usually  selects  that  which  is  most  easily  handled  and  most  quickly 
prepared;  therefore  it  is  not  uncommon  to  see  prospect  shafts 
in  such  regions  cribbed  with  small  timbers  or  even  with  poles. 

As  correct  methods  of  shaft-timbering  require  considerable 
framing,  which  demands  suitable  tools  and  no  little  mechanical 
skill,  we  find  the  prospector  "framing"  his  crib  timbers  with  an 
axe.  The  careful  and  more  experienced  will  strip  the  bark  from 
the  poles  or  timbers  before  placing  them  in  the  mine;  others 
blaze  the  side  next  the  shaft;  while  those  who  care  nothing  for 
the  permanency  of  the  work  will  put  the  sticks  in  the  shaft  with- 


48 


TIMBERING   AND   MINING 


out  removing  any  of  the  bark  at  all.  A  crib  built  with  the  bark 
on  seldom  outlasts  two  years,  and  if  not  renewed  the  shaft  is 
usually  lost. 

Near  Grizzly  Flat,  El  Dorado  County,  California,  the  writer 
saw  a  two-compartment  shaft  nearly  300  ft.  deep  on  the  Mount 
Pleasant  mine.  Climbing  down  the  vertical  ladder  of  this  shaft, 
it  was  observed  that  the  timbers,  which  were  12  X  12  in.  and 
splendidly  framed,  presented  an  unusually  smooth  appearance. 
At  first  it  was  supposed  that  the  timbers  had  been  sawed  and  then 
planed,  but  closer  inspection  showed  that  each  timber  had  been 
hewn  by  a  master  hand  —  probably  by  a  ship  carpenter,  for  no 


FIG.  18.  —  Crib  of  Timbers  in  Shaft 

miner  would  have  ever  taken  such  infinite  pains  to  produce  the 
artistic  results. 

Cribs  are  made  of  either  round  or  sawed  timber,  both  large 
and  small.  The  round  sticks  are  more  commonly  seen.  As  the 
work  progresses,  if  several  feet  can  be  sunk  ahead  of  timbering, 
a  good  set  of  four  pieces  is  placed  in  position  and  firmly  wedged. 
Upon  these  the  crib  is  built  upward  toward  the  surface  to  the 
collar  of  the  shaft,  or  to  meet  the  last  lot  of  timbers  put  in.  Ex- 
cavation then  proceeds  as  before,  and  when  it  has  gone  as  far 
as  is  considered  safe,  the  crib  is  again  commenced  and  built  up 
to  join  the  last  lot.  If  the  ground  is  too  loose  to  admit  of  this, 
the  crib  must  be  built  from  the  top  downward,  and  a  set  put  in 
and  wedged  as  fast  as  room  can  be  made  for  it.  Should  the  ground 


SHAFTS  49 

be  so  loose  or  heavy  as  to  render  this  a  difficult  or  unsafe  job,  it 
were  better  to  employ  some  one  of  the  regular  methods  of  shaft 
timbering  and  not  to  attempt  the  crib. 

The  accompanying  sketch,  Fig.  18,  illustrates  a  crib  of  sawed 
timber  and  the  method  of  framing.  It  is  desirable  to  leave  as 
little  open  space  as  possible  back  of  the  crib  timbers  —  or,  in 
fact,  of  any  timbers  —  in  shaft  sinking  through  loose  ground. 
For  this  purpose  rocks,  waste  timber  ends,  and  often  cordwood, 
are  employed.  It  prevents  the  ground  from  "starting,"  which  is 
very  important. 


Size  and  Division  of  Working  Shafts.      Drainage 

Working  shafts  for  mines  are  made  with  one  or  more  com- 
partments. The  shaft  of  three  compartments  is  the  most  com- 
mon, though  some  small  mining  operations  have  been  successfully 
carried  on  through  a  shaft  having  but  a  single  compartment. 
As  a  matter  of  course,  a  large  mine,  outputting  a  thousand  or 
more  tons  of  rock  daily,  might  be  operated  through  a  single  com- 
partment if  it  were  large  enough.  The  only  reason  this  is  not 
done  is  because  of  the  necessity  of  sustaining  the  rock  masses 
through  which  the  shaft  passes.  Long  experience  has  demon- 
strated that  it  is  extremely  dangerous  to  leave  any  large  rock 
surface  exposed  without  providing  proper  support.  If  rocks 
were  homogeneous,  and  not  divided  as  they  are  into  innumerable 
blocks  by  cleavage,  jointing  and  other  planes,  the  ground  would 
probably  stand  very  well,  and  no  timber  or  other  support  would 
be  required  excepting  such  as  might  be  necessary  to  carry  guides, 
ladders  and  pipes;  but  the  fact  that  all  rocks  are  divided  by  these 
planes  of  jointing,  bedding  and  cleavage,  beside  more  or  less 
numerous  fissures,  renders  it  necessary  that  timber,  steel,  masonry, 
concrete,  or  some  other  artificial  support,  be  employed  to  render 
the  shaft  safe.  In  Mexico  are  some  remarkable  examples  of 
large  shafts.  In  a  few  instances  these  great  excavations  exceed 
2000  ft.  in  depth  and  are  20  or  more  ft.  in  diameter,  being  circular 
or  octagonal  in  form.  The  rocks  are  supported  by  masonry. 
Hoisting  was  accomplished  by  means  of  horse  whims  set  opposite 
the  several  sides  of  the  shafts.  These  great  shafts  are  among 
the  native  engineering  wonders  of  Mexico.  Similar  shafts  have 
been  sunk  in  the  coal  fields  of  northern  China.  Surely  the  men 


50 


TIMBERING   AND   MINING 


who  conceived  and  directed  the  execution  of  the  work  in  making 
these  wonderful  excavations  were  engineers  of  no  mean  order. 
In  the  United  States  few  shafts  have  more  than  four  compart- 
ments, though  there  are  some  in  the  Lake  Superior  copper  region 
having  six.  A  surprisingly  large  tonnage  can  be  hoisted  from  a 
depth  of  3000  ft.  through  a  well-equipped  shaft  of  three  com- 
partments if  the  proper  loading  and  discharging  facilities  be  pro- 
vided. In  consideration  of  the  fact  that  nearly  4000  tons  have 
been  hoisted  daily  through  a  three-compartment  shaft  from  a 
depth  exceeding  1500  ft.  for  months  at  a  time  at  Kimberly, 


FIG.  19.  —  A  Prospector's  Shaft  with  Horse  Whim 

South  Africa,  it  would  seem  that  a  shaft  of  this  description  would 
answer  for  most  requirements  of  mines  in  the  United  States. 
It  is  our  opinion,  however,  that  the  most  complete  shaft  is  one 
of  four  compartments.  Two  compartments  for  hoisting  ore  (and 
waste  when  necessary);  one  compartment  fitted  with  a  special 
cage  for  the  accommodation  of  the  superintendent,  foremen, 
shift  bosses,  pump  men,  skip  tenders,  powder  men,  tool  packers 
and  others  whose  duties  require  frequent  passage  up  or  down 
the  shaft.  This  cage  could  also  be  used  for  the  accommodation 
of  visitors,  who  are  more  or  less  numerous  at  most  mines,  and 
who  are  also  a  source  of  no  little  expense  in  various  ways.  This 
"service"  compartment  might  be  somewhat  smaller  than  the 


SHAFTS  51 

hoisting  compartments,  and  the  cage  in  it  should  be  handled  by 
a  separate  engine.  Through  this  compartment,  also,  the  pumps 
could  be  raised  and  lowered  as  required.  The  fourth  compart- 
ment should  be  somewhat  larger  than  either  of  the  others,  and 
in  it  should  be  placed  the  ventilating  pipes,  water  and  compressed- 
air  columns,  and  steam  pipes,  if  steam  is  employed  to  operate 
pumps,  which  practice  in  large  mines  is  being  generally  discon- 
tinued, compressed  air  or  electricity  having  to  a  great  extent 
replaced  steam.  If  Cornish  pumps  are  in  use  the  pump  rod 
should -be  placed  in  this  fourth  compartment;  and  here,  too,  are 
the  ladder  ways. 

A  shaft  equipped  as  here  suggested  affords  the  highest  degree 
of  utility  possible.  Hoisting  can  be  carried  on  uninterruptedly; 
the  executive  staff  can  descend  or  ascend  the  shaft  at  any  time 
without  interfering  with  hoisting  operations;  the  pipes  for  air 
and  water  are  in  a  roomy  compartment  with  frequent  platforms, 
enabling  any  necessary  work  there  to  be  done  without  interruption, 
which  saves  time  and  consequently  money.  In  mines  where 
drainage  is  accomplished  by  bailing  with  buckets  or  skips,  it 
may  be  advisable  to  put  the  service  cage  in  the  ladder-way  com- 
partment and  place  the  bailing  skip  in  the  third  compartment. 
Where  a  very  large  volume  of  water  must  be  handled  by  bailing, 
it  has  been  economically  accomplished  by  providing  a  shaft  of 
two  compartments  for  this  purpose  alone.  In  the  Pennsylvania 
coal  region,  mines  are  equipped  with  such  shafts,  in  which  the 
large  bailing  skips,  operated  by  electricity,  descend,  fill  and 
are  hoisted  and  discharged  automatically,  no  attendant  being 
required,  the  engineer  on  duty  attending  to  the  entire  electric 
installation  connected  with  the  mine,  having  no  special  work  to 
perform,  so  far  as  the  bailing  skips  are  concerned.  These  skips 
are  run  in  balance,  and  operated  night  and  day  regularly,  hoist- 
ing and  discharging  their  load  of  water.  A  skip  of  1500  gal. 
capacity,  run  at  a  speed  of  even  1000  ft.  per  minute,  will  raise  a 
very  large  amount  of  water  fron  a  mine  3000  ft.  deep  in  24  hours. 
Generally  speaking,  bailing  is  a  less  expensive  method  of  draining 
a  mine  through  a  shaft  than  by  any  method  of  pumping,  if  the 
bailing  installation  be  properly  equipped.  An  inefficient  bail- 
ing plant,  however,  will  prove  an  expensive  method  of  Jiandling 
water. 


52  TIMBERING  AND  MINING 

Positions  of  Temporary  Hoisting  Plant  and  Permanent 

Plant 

A  word  about  the  sinking  plant  and  we  will  then  consider 
the  various  means  of  shaft  sinking,  the  methods  of  doing  the  work, 
and  of  timbering  under  the  conditions  usually  met  in  Western 
metal  mines.  The  sinking  plant  should  be  of  such  capacity  as 
will  permit  the  shaft  to  be  carried  to  a  reasonable  depth,  say  400 
to  500  ft.  This  machine,  of  about  10  to  12  h.p.,  must  have 
double  cylinders,  and  should  be  in  every  way  a  first-class  hoisting 
machine,  and  one  which  can  be  absolutely  depended  upon  to 
work  promptly  and  safely.  It  is  a  mistake  to  think  that  any  kind 
of  an  engine  will  do  for  shaft  sinking.  There  is  no  more  dangerous 
branch  of  mining  work  than  that  of  shaft  sinking  and  the  men 
below  should  be  safeguarded  as  far  as  possible.  When  a  depth 
of  400  to  500  ft.  has  been  attained,  it  is  good  practice  to  replace 
the  small  hoist  with  one  capable  of  going  to  1500  or  2000  ft.,  the 
small  machine  being  placed  under  cover  to  be  used  later  under- 
ground in  sinking  winzes,  or  to  deepen  the  shaft  below  an  estab- 
lished level.  The  machine  taking  its  place  should  be  of  25  or 
30  h.p.,  not  necessarily  a  fast-winding  engine,  but  a  capable  and 
safe  one.  With  this  the  sinking  may  be  continued  to  1500  ft.  or 
more,  levels  opened,  and  connections  made.  In  the  meantime, 
the  knowledge  gained  of  the  actual  resources  and  probable  life 
of  the  mine  enables  the  management  or  consulting  engineer  to 
determine  the  character  of  the  permanent  plant  and  provide  for 
its  installation.  In  anticipation  of  this,  it  is  necessary  at  the 
time  of  commencing  the  shaft  to  select  a  site  for  the  temporary 
hoist  which  will  later  admit  of  the  large,  permanent  hoisting 
machinery  and  head-frame  being  placed  in  position  without 
interfering  with  the  operation  of  the  smaller  plant,  which  may  be 
run  almost  up  to  the  moment  of  placing  the  new  plant  in  opera- 
tion. With  this  in  view,  it  is  good  practice  to  place  the  temporary 
hoists  —  both  the  first  and  second  plants  —  either  on  the  opposite 
side  of  the  shaft  from  the  site  of  the  permanent  plant,  or  at  a 
point  opposite  the  end  of  the  shaft.  In  some  cases  the  temporary 
plant  has  been  set  between  the  shaft  and  the  site  of  the  permanent 
plant,  the  smaller  engine  being  set  opposite  the  compartment  in 
which  the  service  cage  is  afterward  placed,  this  engine,  or  another, 
being  used  for  operating  the  service  cage.  As  it  is  never  called 


SHAFTS 


53 


upon  to  hoist  a  very  heavy  load,  this  engine  would  probably  have 
sufficient  power  to  operate  the  service  cage  to  a  far  greater  depth 
than  would  be  economical  in  hoisting  waste  or  ore. 


FIG.  20.  —  Steel   Head-frame  at  Old   Dominion  Mine,   Globe,  Arizona 

The  topography  about  the  shaft  will,  of  course,  be  a  factor  in 
determining  the  position  of  the  hoisting  engines,  and  the  height 


54  TIMBERING  AND   MINING 

and  shape  of  the  head-frame,  but  the  importance  of  future  per- 
manent installation  cannot  be  neglected,  and  it  is  the  part  of 
wisdom  to  plan  from  the  beginning  with  these  facts  in  mind. 
Fig.  20  illustrates  the  modern  steel  head-frame  at  the  Old  Do- 
minion Mine,  Arizona. 

Size  of  Shaft  Compartments 

Not  less  important  than  the  number  of  compartments  in  a 
shaft  through  which  a  large  amount  of  rock  is  to  be  hoisted,  is 
the  size  of  the  compartments.  In  California  practice  it  has  been 
the  custom  to  make  shafts  4  X  4^  or  4  X  5  ft.  clear,  inside  the 
timbers,  the  greater  number  of  shafts  having  two  compartments. 
This  is  antiquated  practice  and  has  in  more  recent  years  been 
succeeded  by  shafts  of  somewhat  more  liberal  dimensions,  usually 
with  three  compartments.  It  should  be  remembered,  however, 
that  there  is  probably  not  a  mine  in  California  where  1000  tons 
of  ore  are  hoisted  through  a  single  shaft  in  24  hours,  whereas 
there  are  mines  elsewhere  where  two  to  four  times  this  amount 
of  ore  is  hoisted  every  day  through  a  single  shaft.  This  is  the 
case  at  Butte,  Montana,  at  some  shafts  in  the  'Lake  Superior 
Copper  region,  the  gold  mines  of  the  Rand,  South  Africa,  at  the 
Kimberley  diamond  mines,  and  at  a  great  many  coal  mines  in 
Eastern  states.  It  is  therefore  no  novelty  to  hoist  2000  or  4000 
tons  of  rock  or  coal  through  a  single  shaft  in  24  hours,  but  this 
feat  demands  a  shaft  with  at  least  two  hoisting  compartments 
of  liberal  size. 

On  the  Rand,  some  of  the  earlier  large  shafts  were  made 
from  4  X  6  to  4J  X  6  ft.,  according  to  Thomas  H.  Leggett,  but 
these  dimensions  were  found  inadequate,  and  the  later  shafts 
were  5  X  6  ft.  with  a  pump  and  ladder-way  compartment  6  X  6 \  ft. 
For  large  tonnage,  not  only  large  shafts,  but  fast-winding  engines, 
are  essential.  Engines  are  in  use  in  scores  of  places  that  wind  a 
load  of  from  three  to  ten  tons  at  speeds  varying  between  1000 
and  6000  ft.  per  minute.  »In  California,  the  custom  of  sinking 
working  shafts  of  relatively  small  sectional  area  is  no  doubt 
due  to  the  fact  that  many  of  the  most  noted  shafts  in  that  state 
are  on  the  Mother  Lode,  and  the  heavy,  swelling  ground  in  those 
mines  has  led  the  mine  managers  to  sink  small  shafts  to  enable 
them  to  better  hold  the  ground.  Most  of  the  old  shafts  were 
sunk  in  the  fissure,  and  few  miners,  who  have  never  had  experi- 


SHAFTS  55 

ence  in  these  shafts,  realize  the  difficulties  to  be  overcome,  not  so 
much  in  sinking  them  originally  as  in  keeping  them  open  later. 
Among  the  noted  old  shafts  of  the  description  mentioned  as  on 
the  Mother  Lode  of  California  are  the  original  Keystone,  the  Wild- 
man,  the  Eureka,  the  Central  Eureka,  the  south  shaft  of  the 
Kennedy,  the  Hardenburgh,  the  original  shaft  of  the  Gwin  mine, 
and  several  others  of  less  note.  All  of  these  shafts  were  sunk  in 
the  fissure,  and  each  of  them  proved  a  source  of  constant  expense 
in  keeping  them  open. 

In  more  recent  years  it  has  been  considered  the  best  mining 
practice  to  sink  working  shafts  in  the  Mother  Lode  region  of 
California  either  vertically,  starting  in  the  hanging  wall  country, 
like  the  Kennedy  east  shaft,  the  Gwin  mine  east  shaft,  the  Oneida 
east  shaft,  and  the  Cross  shaft  of  the  Utica-Stickle  mine;  or  in- 
clined, in  the  country  rock,  as  in  the  case  at  the  Argonaut  mine 
near  Jackson.  This  shaft,  commencing  in  the  hanging  wall,  is 
sunk  at  a  uniform  angle  of  63  degrees,  in  which  it  has  a  decided 
advantage  over  those  sunk  in  the  fissure,  which  always  varies 
more  or  less  in  the  angle  of  dip,  resulting  in  an  unsatisfactory 
shaft.  It  is  advisable,  therefore,  in  view  of  what  has  been  learned 
from  the  practical  and  expensive  experience  of  many  careful 
operators  in  widely  separated  parts  of  the  world,  to  make  work- 
ing shafts  of  liberal  size,  and  to  avoid  sinking  them  in  a  vein  or 
fissure  if  future  trouble  is  to  be  avoided.  The  first  cost  of  sinking 
a  shaft  through  country  rock  is  almost  always  more  than  where 
the  sinking  is  done  in  the  vein,  but  if  this  fissure  with  depth 
should  prove  to  be  in  swelling  ground,  the  extraordinary  expense 
of  keeping  the  shaft  in  repair  within  the  first  five  years  would 
more  than  meet  the  increased  expense  of  sinking  in  the  hard 
country  rock.  The  methods  adopted  to  keep  open  the  shafts 
sunk  in  heavy  ground  will  be  taken  up  later  and  explained  in 
detail. 

The  Collar 

When  the  site  for  a  shaft  has  been  selected  with  due  regard 
to  the  various  considerations  already  set  forth,  the  first  thing 
to  be  done  is  to  take  the  necessary  steps  to  make  the  collar  of 
the  shaft  permanently  secure.  It  is  not  always  possible  to  locate 
the  shaft  at  a  point  where  solid  rock  outcrops.  Sometimes 
loam,  clay  or  gravel  is  found  to  a  depth  of  several  feet  where  it 


56 


TIMBERING   AND   MINING 


is  desired  to  start  the  shaft.  The  writer  sunk  a  prospecting  shaft 
of  two  compartments  in  Tuolumne  County,  California,  several 
years  ago.  This  shaft  was  started  on  a  flat,  where  the  surface 
material,  to  a  depth  of  13  ft.,  was  loam  and  clay.  This  earth, 
when  dry,  was  hard  enough  to  make  it  economical  to  blast  it  with 
low  powder,  but  when  wet  a  ton  might  easily  ooze  through  a 
knothole.  Necessarily,  the  collar  of  this  shaft  needed  careful 
preparation,  and  steps  were  taken  to  render  the  subsequent 
work  below  secure.  Heavy  mudsills  were  laid  on  a  bed  of  coarse 
broken  rock,  and  upon  these  sills  the  main  supporting  timbers 
of  the  first  few  sets  were  placed.  The  shaft  was  carried  to  a 


1 1  111  IF 
FIG.  21. —  Head-frame  built  on  Framework  to  secure  Dump. 

depth  of  20  ft.  and  the  sets  put  in  place,  the  wall  plates  being 
suspended  by  permanent  straight  hanging-bolts  made  of  1-in. 
iron.  When  in  place,  the  space  between  the  lagging  (of  2-in. 
plank)  and  the  earth  and  rock  walls  was  filled  in  with  cordwood 
and  broken  rock,  but  I  would  never  advise  a  repetition  of  this, 
nor  repeat  it  myself.  In  that  instance  it  was  done  to  save  the 
shaft,  as  a  heavy  and  unexpected  rain  threatened  to  destroy  all 
that  had  been  done  by  the  caving  of  the  soft,  wet  clay.  Prompt 
filling  saved  the  shaft,  and  there  was  little  choice  of  method. 
This  was  a  prospecting  shaft,  and  all  was  done  there  that  the 
situation  seemed  to  demand.  As  the  surface  about  the  shaft 
was  nearly  flat,  there  was  no  suitable  place  to  dump  rock;  con- 


SHAFTS  57 

sequently  a  timber  frame  was  built,  raising  the  collar  of  the 
shaft  about  nine  feet  above  the  surface,  and  around  this  the  rock 
from  the  shaft  was  dumped,  the  head-frame  being  built  upon 
the  timber  frame.  (See  Fig.  21.) 

In  the  case  of  a  large  and  expensive  shaft,  planned  to  go  to 
the  depth  of  several  hundred  or  several  thousand  feet,  nothing 
would  under  any  circumstances  justify  any  such  makeshift 
method  as  that  above  described.  It  may  occasionally  be  found 
necessary  to  carry  the  shaft  up  into  the  head-frame  for  the  pur- 
pose of  securing  dump  room,  or  for  some  other  purpose,  but  the 
collar  of  the  shaft  must  be  made  permanently  secure.  The  best 
manner  of  doing  this  is  to  excavate  a  pit  to  bed  rock  in  the  soil, 
clay,  or  loose  rock,  of  such  size  as  will  admit  of  the  building  of  a 
solid  wall  of  concrete  or  masonry  about  the  proposed  shaft. 
The  inside  dimensions  of  the  structure  thus  built  should  be  such 
that  the  regular  shaft  sets  may  be  placed  therein,  in  perfect 
alignment  with  those  that  are  to  be  placed  in  the  shaft  beneath. 
This  concrete  or  masonry  wall  should  be  set  deep  enough  in  the 
solid  rock  to  act  also  as  a  dam  to  the  passage  of  surface  water, 
thus  keeping  the  shaft  from  being  flooded  from  this  cause  during 
the  wet  season.  The  wall  also  affords  a  substantial  foundation 
for  the  head-frame  —  the  walls  being  built  back  from  those  sur- 
rounding the  shaft,  where  needed,  to  support  the  superstructure 
—  head-frame,  ore  bins  and  often  the  rock  breaker  as  well. 

When  the  wall  has  been  completed,  the  first  shaft  timbers 
are  placed,  extending  beyond  the  limits  of  the  shaft,  the  ends 
resting  solidly  upon  the  wall.  Either  the  ends  or  the  wall  plates 
may  be  so  disposed.  In  some  cases  both  ends  and  wall  plates 
are  thus  extended,  being  held  in  position  by  drift  bolts.  Care 
must  be  taken  in  the  planning  of  this  structure  that  the  upper- 
most timbers  of  the  set  are  not  higher  than  the  level  of  the  collar 
of  the  shaft.  If  both  wall  and  end  plates  are  extended  to  rest 
upon  the  wall,  it  is  the  better  plan  to  place  the  ends  underneath, 
the  wall  plates  resting  on  top  of  them;  then  a  "filling  piece" 
may  be  let  in  on  the  top  of  the  ends,  between  the  wall  plates, 
thus  bringing  all  timbers  flush  at  the  collar.  Of  course,  the 
timbers  may  be  framed  so  as  to  bring  them  flush,  but  it  seems 
the  best  practice  to  allow  to  these  surface  timbers  their  full 
strength. 


58  TIMBERING   AND  MINING 

Hanging-bolts 

Having  placed  the  collar  set,  the  sets  beneath  may  be  sus- 
pended in  position  by  means  of  straight  hanging-bolts,  which 
are 'to  remain  permanently.  One  important  matter  in  the  use 
of  hanging-bolts,  either  the  permanent  straight  bolts  or  the  sets 
of  hooks,  is  the  use  of  washers  of  large  diameter  and  thickness. 
Never  use  a  washer  less  than  four  inches  diameter,  even  where 
small  timbers  are  used  —  8  X  8  in.  for  instance,  and  if  the  timbers 
are  larger  use  4J  or  5-in.  washers.  Often  heavy  downward 
pressure  develops  after  a  shaft  has  been  sunk  some  time,  and  the 
stress  upon  the  hanging-bolts  causes  the  washers  to  sink  into  the 
pine  wood  from  J  to  J  in.,  so  that  a  shaft  may  settle  at  one  end 
or  side,  or  all  round,  for  that  matter,  an  inch  or  two  therefrom 
in  four  or  five  sets.  When  this  occurs  the  timbers  may  sometimes 
be  forced  back  into  position  by  use  of  the  hydraulic  jack,  or  even 
the  ordinary  jack-screw,  but  it  involves  expense  and  loss  of  time, 
which  may  have  been  avoided  by  taking  the  precaution  to  use 
large  washers.  This  suggestion  is  the  outcome  of  experience 
in  the  use  of  small  washers. 

Another  precaution  is  to  use  hanging-bolts  of  not  less  than 
three-quarter  iron  —  seven-eighths  being  better;  and  where  the 
shaft  is  large  and  the  ground  believed  to  be  heavy,  use  1-in. 
iron.  This  admits  of  the  cutting  of  heavy  threads  which  will 
not  readily  "strip,"  and  the  hooks  will  be  far  less  likely  to 
straighten  out  or  break,  as  they  sometimes  do  when  light  iron 
is  used  for  bolts. 

The  Cross-Head  in  Sinking  Shafts  with  a  Bucket 

Before  proceeding  with  the  work  of  shaft  excavation  we  will 
first  consider  some  of  the  methods  of  performing  this  work  in 
an  expeditious  and  economical  manner  with  reference  to  surface 
equipment.  Hoisting  from  vertical  shafts,  while  sinking  is  in 
progress,  is  generally  done  with  a  bucket,  though  occasionally 
with  a  low  skip.  The  skip  is  more  commonly  used  in  inclined 
shafts  than  in  those  that  are  vertical.  The  bucket  has  advan- 
tages over  the  skip,  however.  It  is  lighter,  and  therefore  easier 
to  handle.  It  may  be  placed  anywhere  on  the  bottom  of  the 
shaft  while  being  filled  by  the  shovelers,  which  is  not  the  case 
with  a  skip.  Where  the  latter  is  used  in  a  three-compartment 


SHAFTS  59 

shaft,  the  skip  should  be  operated  in  the  center  compartment. 
In  shafts  where  cages  and  skips  are  used,  hoisting  of  rock  from 
sinking  is  often  done  by  a  bucket  swung  beneath  the  cage  or 
skip.  Of  course,  this  necessitates  sufficient  clearance  room  in 
the  head-frame.  As  buckets  sometimes  are  carelessly  started 
from  the  bottom,  they  swing  about  in  the  shaft  and  become  a 
great  menace  to  men  below.  The  danger  from  this  source  may 
be  obviated  in  a  great  degree,  if  not  altogether,  by  placing  guides 
in  the  shaft  and  employing  what  is  known  as  a  cross-head,  which, 
running  in  guides,  prevents  the  bucket  from  swinging  danger- 
ously in  the  shaft. 

The  cross-head  is  a  simple  frame  of  timbers  which  may  be 
easily  made  by  any  carpenter,  or  even  a  miner  handy  with  tools. 
The  ironwork  can  be  turned  out  by  any  mine  blacksmith.  They 
are  made  after  various  ideas,  almost  as  various  as  the  number  of 
men  who  make  them.  One  point,  however,  must  not  be  forgotten. 
The  cross-head  should  be  twice  as  high  as  it  is  wide,  or  it  may 
jam  against  the  guides  and  cause  a  serious  accident;  such  things 
are  not  unknown.  Some  take  two  pieces  of  4  X  6  in.  lumber, 
in  length  a  little  short  of  the  distance  between  the  inner  faces 
of  the  guides.  These  are  placed,  say,  6  ft.  apart.  To  each  side 
of  these  are  spiked  or  bolted  cross-pieces  in  the  form  of  the  letter 
X,  the  ends  extending  beyond  the  face  of  the  guides,  forming 
a  groove  which  keeps  the  cross-head  in  place.  This  method  of 
building  a  cross-head  is  not  as  strong  as  some  others. 

In  the  opinion  of  the  writer  the  most  simple  and  enduring 
cross-head  is  made  by  forming  a  rectangular  frame  of  four  pieces 
of  lumber,  carefully  sawed  and  strengthened  by  iron  bolts  pass- 
ing vertically  through  the  structure  from  top  to  bottom,  the 
horizontal  pieces,  top  and  bottom,  being  4  X  6  in.,  the  wider 
dimension  being  uppermost  —  the  size  of  these  pieces  being 
determined  by  that  of  the  guides.  Between  these  insert  two 
4  X  6  in.  uprights.  A  small  mortise  may  be  made  in  the  hori- 
zontal members,  into  which  may  be  fitted  the  tenons  framed  on 
the  uprights.  Auger  holes  are  bored  at  the  center  of  each 
horizontal  stick,  through  which  the  rope  is  passed.  The  grooves 
may  be  made  by  securely  bolting  to  the  four  corners  on  each  side 
J-m-  steel  plates  which  project  at  least  4  in.  at  the  side  of  the 
guide  timbers.  Or  a  piece  of  channel  steel  may  be  firmly  bolted 
to  both  edges  of  the  cross-head.  These  bolts  require  double  nuts, 


60 


TIMBERING   AND   MINING 


y 


\ 


1 1  II 


Guide 


FIG.  22 


SHAFTS 


61 


so  that  they  may  not  become  loosened  by  use.  The  upper  and 
lower  edges  of  this  guide  runner  should  be  turned  back  from  the 
guides  so  as  to  avoid  any  inequalities  on  the  guides.  The  accom- 
panying sketch,  Fig.  22,  shows  the  method  of  constructing  a 
cross-head  of  this  kind.  Underneath  the  lower  bar  will  be  ob- 
served a  clip  upon  the  hoisting  rope.  This  should  be  securely 
fastened.  Its  function  is  to  lift  the  cross-head  when  the  bucket 
is  hoisted.  The  clip  should  be  placed  so  far  above  the  bucket 
that  it  will  be  out  of  reach  of  men  riding  the  bucket.  Failure  to 
anticipate  this  has  caused  injury  to  men  by  their  being  struck 
by  the  cross-head. 


FIG.  23 

To  prevent  the  cross-head  from  dropping  off  the  guides  at  the 
bottom  of  the  shaft,  blocks  should  be  spiked  to  the  shaft  timbers 
on  each  side  of  the  guides,  and  upon  these  the  descending  cross- 
head  will  rest  when  the  last  set  of  timbers  is  reached.  An  im- 
provement on  this  suggestion  would  be  the  construction  of  a 
movable  stop  or  bumper,  by  securely  bolting  two  blocks  to  a 
piece  of  3  X  8  in.  lumber,  in  such  a  manner  that  the  bumpers 
may  be  placed  like  a  saddle  around  the  guides,  the  3  X  8-in. 
piece  resting  on  the  end  plate  or  divider  of  the  shaft  set,  as 
shown  in  Fig.  23.  As  the  work  of  sinking  progresses,  these 
bumpers  may  be  moved  downward,  set  by  set,  as  often  as  nec- 
essary. 


62 


TIMBERING   AND   MINING 


Stull  Methods  in  Many  Small  Mines  of  the  Cobalt  District, 

Ontario 

Mr.  Algernon  Del  Mar  has  contributed  the  following  regarding 
the  methods  of  timbering  small  shafts  in  hard  rock  in  the  Cobalt 
region  of  Ontario,  Canada: 

.  "Shafts  for  prospecting  differ  in  size  and  equipment  accord- 
ing to  the  financial  abilities  of  the  operators  and  the  size  and 
character  of  the  veins  and  the  walls  enclosing  the  veins.  Many 
of  the  shafts  in  the  West  are  4X4  ft.  inside,  and  I  had  occasion 
to  visit  one  in  Norway  20  X  20  ft.  inside.  These  are  extremes, 
and  between  these  there  is  a  safe  mean.  If  the  property  under 


FIG.  24.  —  Small  Shaft  in  hard  Ground 

consideration  has  a  showing  warranting  development  to  a  moder- 
ate depth,  the  shaft  should  be  timbered,  or  the  ground  taken 
out  to  allow  timbering  when  it  is  necessary,  unless  the  ground  is 
exceptionally  firm,  when  end  stulls  for  guide  timbers,  or  ties  for 
track,  will  alone  be  necessary.  A  4  X  5  ft.  shaft  will  do  very 
well  for  50  or  100  ft.,  and  when  timbered  will  give  a  space  3  X  4  ft. 
for  a  bucket,  but  no  space  for  a  ladder-way.  A  6  X  8  ft.  shaft, 
while  wide  enough,  is  a  little  short  in  length  for  a  good  second 
compartment.  A  better  size  is  6  X  9  ft.  outside.  This  will 
permit,  with  10-in.  timbers  and  lagging,  a  compartment  4  X  4  ft. 
for  bucket,  skip  or  cage,  and,  with  12  in.  for  brattice  between 
compartments,  will  give  one  compartment  2  X  4  ft.  for  ladder 
and  pipe-way.  A  two-compartment  permanent  shaft  should  be 


SHAFTS 


63 


a  little  larger,  but  a  6  X  9  ft.  shaft  will  answer  for  prospecting  to 
400  or  500  ft.,  and  if  properly  equipped  with  hoisting  machinery 
should  supply  a  40-stamp  mill. 

"The  timbering  for  this  shaft  will  vary  with  the  different 
kinds  of  ground  encountered,  and  also  with  the  inclination  of  the 
shaft.  If  the  ground  has  a  tendency  to  cave  or  run,  it  will  have 
to  be  cribbed;  if  it  stands  fairly  well,  it  may  be  timbered  with 
square-sets  lagged  on  the  sides  that  are  loose.  If  the  walls  cement 
on  exposure  to  air,  as  in  the  desert  regions  of  the  West,  very  little 
timbering  other  than  the  collar  sets  is  required.  Where  the  two 
walls  are  firm  and  not  easily  broken  and  the  shaft  vertical,  I  have 
found  a  compromise  method  to  answer  the  purpose  admirably, 
and  with  less  expense  than  the  ordinary  square- sets.  This  is  to 


FIG.  25 

cut  hitches  for  the  stull  timbers  and  on  them  cut  a  dap  in  which 
rests  the  wall  plate.  Place  corner  posts,  wedge  and  lag  in  the 
usual  way.  This  sort  of  shaft  is  preferable  to  the  ordinary  square- 
set  style  when  sinking  in  ore,  for  the  ground  may  then  be  stoped 
around  the  shaft  without  displacing  the  timbers,  for  the  stulls 
are  firmly  wedged  against  the  walls.  I  found  this  method  to  be 
quicker  and  requiring  less  knowledge  on  the  part  of  the  miners 
than  placing  square-sets,  for  the  hitches  could  be  cut  while  the 
machines  were  at  work  on  the  other  side  of  the  shaft,  and  the 
timbers  could  be  wedged  in  place  without  interrupting  the  work 
at  all.  The  sketches,  Figs.  24  and  25,  show  the  practice  in  Cobalt 
district,  Ontario,  Canada,  where  the  wall  rocks  are  hard.  The 
method  has  been  found  satisfactory  in  that  district." 


CHAPTER  VIII 

BUCKET   DUMPING 

Methods  at  Vertical  Shafts 

HAVING  described  the  cross-head,  its  usefulness  and  the  manner 
of  constructing  it,  we  may  now  consider  the  various  means 
employed  to  dump  buckets  upon  their  reaching  the  surface. 
At  many  mines  the  "trip-rope"  is  employed,  and  this  device 
is  certainly  a  convenient  one,  as  it  can  be  quickly  and  safely 
attached  and  the  buckets  promptly  dumped.  All  rock  buckets 
have,  or  should  have,  a  ring  securely  attached  to  an  eye  in  the 
bottom.  The  trip-rope  is  suspended  at  some  point  overhead — • 
this  point  is  determined  by  the  direction  in  which  it  is  desired 
to  dump  the  bucket,  and  also  by  the  distance  from  the  shaft  at 
which  the  rock  is  to  fall.  It  may  be  dumped  directly  into  a 
car,  into  a  bin  provided  with  a  chute,  or  on  the  ground,  as  may 
be  desired.  Often  it  is  necessary  to  hoist  both  ore  and  waste 
from  the  shaft,  and  as  a  matter  of  course  it  is  desirable  to  keep 
ore  and  waste  separate,  when  possible.  To  do  this  it  is  not  an 
uncommon  practice  to  have  two  trip-ropes  —  one  in  front,  the 
other  in  the  rear  of  the  shaft,  the  ore  being  dumped  at  one  place, 
the  waste  at  the  other.  Where  the  rock  is  dumped  into  a  bin, 
it  is  generally  necessary  to  dump  both  ore  and  waste  into  it,  so 
that  whichever  is  sent  up  first  must  be  removed  before  the  other 
class  of  material  is  hoisted.  This  can  usually  be  arranged  with- 
out difficulty. 

The  employment  of  the  trip-rope  calls  for  an  attendant  to  be 
always  on  hand  to  close  the  door  over  the  shaft  (it  is  necessary 
that  every  vertical  shaft  or  those  sunk  at  a  high  angle  —  over 
40°  —  be  provided  with  a  door  to  insure  the  safety  of  men  work- 
ing below),  to  put  the  hook  at  the  end  of  the  rope  into  the  ring 
beneath  the  bucket,  and  to  raise  the  door  before  the  bucket  can 
again  descend  into  the  shaft.  At  many  shafts  this  is  not  an 
undesirable  feature,  as  the  top-man  is  at  other  times  otherwise 

64 


BUCKET  DUMPING 


65 


FIG.  26 


66  TIMBERING  AND  MINING 

continuously  employed.  He  assists  the  carpenter  in  framing 
timbers;  or  acts  as  helper  to  the  blacksmith;  trams  cars  to  the 
dump;  keeps  up  the  fire  if  steam  power  is  used;  brings  lagging 
and  timbers  to  the  shaft,  and  is  made  generally  useful. 

Before  leaving  the  top-man  and  the  trip-rope  it  is  well  to 
say  that  the  hook  attached  to  the  end  of  the  rope  should  be 
provided  with  an  extension  handle,  as  it  were  — •  a  straight  pro- 
jection from  the  hook  beyond  the  loop  where  it  is  attached  to 
the  rope.  This  will  enable  him  to  quickly  catch  the  hook  into 
the  ring  without  danger  of  injury  to  his  hand.  While  the  trip- 
rope  is  a  convenient  means  of  dumping  buckets,  and  is  the  least 
troublesome  and  least  expensive  to  install,  there  are  other  means 
of  dumping  buckets  automatically  in  which  no  top-man  is  re- 
quired, other  than  the  engineer,  who  is  the  only  person  about  on 
the  surface.  This,  of  course,  applies  to  prospecting  shafts  being 
sunk  with,  perhaps,  limited  means,  and  where  it  is  desirable  that 
every  dollar  shall  be  expended  economically.  By  putting  a  little 
more  money  in  the  top  arrangements  one  man  can  perform  all 
the  work  of  hoisting,  bucket  dumping  and  lowering  the  buckets 
into  the  mine  without  the  need  of  calling  upon  the  services  of 
any  one  else  employed  on  the  surface.  Indeed,  we  have  seen 
prospects  where  one  man  on  top  found  time  to  do  all  of  the  top 
work,  including  blacksmithing,  timber  framing,  hoisting,  tram- 
ming, and  general  work,  but  usually  such  a  man  has  a  financial 
interest  in  the  enterprise,  and  is  working  no  more  than  two  or 
three  men  on  a  shift  below.  It  shows,  however,  what  a  willing 
man  can  do. 

There  are  several  schemes  for  accomplishing  this  work  of 
automatically  dumping  a  bucket  at  the  surface,  and  the  arrange- 
ment may  be  placed  in  either  a  four-post  or  a  two-post  frame. 

The  accompanying  illustrations,  Figs.  26  and  27,  depict  the 
manner  of  operating  these  devices,  either  of  which  is  simple  and 
easily  made  and  operated.  Fig.  26  shows  a  bucket  with  an  ex- 
tended chime  at  the  bottom.  It  is  made  of  boiler  plate,  riveted 
in  the  usual  fashion.  The  door  A  is  hung  on  heavy  strap  hinges 
at  F.  When  open  the  upper  edge  of  the  door  rests  against  a 
timber  at  B.  It  will  be  noticed  that  to  this  door  is  attached  a 
rope,  D,  leading  to  the  engine-room,  where  it  is  within  easy 
reach  of  the  engineer.  It  is  counterbalanced  by  a  weight  at  the 
end  of  the  rope  in  the  engine-room.  The  door  remains  open  at 


BUCKET  DUMPING 


67 


FIG.  27 


68  TIMBERING  AND  MINING 

all  times,  except  when  a  bucket  is  about  to  be  dumped.  The 
engineer  raises  the  bucket  until  it  will  clear  the  door.  Atten- 
tion is  called  to  the  necessity  for  sufficient  head  room  between 
the  top  of  the  door  and  the  sheave,  to  enable  the  bucket  to  clear 
the  door.  When  the  bucket  is  clear  of  the  sweep  of  the  door, 
as  indicated  by  the  dotted  curve  G,  the  engineer  gives  the  rope 
a  quick  jerk,  which  causes  the  door  to  start  forward.  Passing 
its  center  of  gravity  it  drops  across  the  shaft,  resting  on  the  tim- 
ber at  T.  Bolted  to  the  upper  side  of  the  door  is  a  heavy  iron 
strap  with  a  projecting  lug  1  in.  high,  at  E.  The  bucket  is 
lowered  and  slides  downward  a  few  inches,  the  chime  catching 
on  the  lug,  and  the  bucket  is  overturned,  dumping  into  the 
chute  H,  or  directly  into  a  car  standing  at  the  chute.  This 
device  works  well,  and  is  in  use  at  many  places,  but  I  think 
the  dumping  scheme  shown  in  Fig.  27  is  better,  in  that  it  permits 
the  door  to  be  closed  at  any  time,  whether  the  bucket  be  below 
in  the  shaft,  or  suspended  above  the  door. 

This  figure,  No.  27,  illustrates  a  two-post  frame,  to  the  front 
of  whicn  is  attached  a  structure  of  lighter  timbers  to  support 
the  door  and  chute.  The  cross-head  is  at  X,  with  the  bucket 
suspended  beneath.  Under  the  bucket,  and  secured  by  a  short 
rope  or  chain  to  the  ring  in  its  bottom,  is  a  block  of  wood,  0. 
The  apron  or  door  D  is  hinged  at  A,  resting  at  the  upper  edge 
on  the  timber  just  back  of  E,  when  down,  and  on  the  timber 
beneath  B,  when  up.  The  door  is  raised  and  lowered  by  means 
of  the  light  rope  H,  which  passes  over  the  pulley  at  B.  In  this 
apron  at  its  center,  and  extending  from  its  upper  edge  to  near 
its  middle,  is  a  slot,  indicated  in  the  shaded  part  of  the  apron 
at  E.  This  slot  is  directly  opposite  the  hoisting  rope,  so  that 
when  the  bucket  is  raised  from  the  shaft  to  a  height  sufficient 
for  the  bottom  to  clear  the  top  of  the  door,  the  latter  may  be 
lowered,  the  slot  in  the  door  straddling  the  rope  under  the  bucket. 
The  engineer  then  lowers  the  bucket  until  it  reaches  the  door, 
down  which  it  commences  to  slide,  but  is  finally  arrested  by  the 
block,  which,  being  too  large  to  pass  the  slot,  causes  the  bucket 
to  overturn,  dumping  into  the  chute  C.  The  guides  are  repre- 
sented by  G.  The  main  members  of  the  head-frame  are  repre- 
sented by  P.  The  line  of  the  hoisting  rope  from  the  sheave  to 
the  winding  reel  is  seen  at  F,  and  R  is  the  line  of  resultant  strain. 
It  is  suggested  that  the  door,  as  shown  in  the  drawing,  is  inclined 


BUCKET  DUMPING  69 

at  too  low  an  angle.  Not  that  it  will  fail  to  cause  the  bucket  to 
dump,  but  for  the  reason  that  it  requires  the  rope  beneath  the 
bucket  to  be  unnecessarily  long,  so  that  the  bucket  in  dumping 
drops  too  far  down  into  the  chute.  If  the  door  were  2  ft.  higher, 
being  still  hinged  at  A,  it  would  undoubtedly  work  better. 

When  the  bucket  has  been  dumped,  the  engineer  raises  it 
until  its  bottom  is  above  the  top  of  the  door,  when  the  latter 
may  be  lifted  and  the  bucket  again  lowered  into  the  mine. 

Methods  at  Inclined  Shafts 

We  have  described  at  some  length  the  use  of  the  cross- head 
and  devices  for  dumping  buckets  at  vertical  shafts.  Probably 
by  far  the  greater  number  of  shafts  —  prospecting  shafts,  at  any 
rate  -—  are  inclined,  and  automatic  dumping  devices  are  as  neces- 
sary at  inclined  as  at  vertical  shafts.  Numerous  are  the  con- 
trivances introduced  for  this  purpose.  At  a  few  inclined  shafts, 
sunk  at  high  angle  —  above  65°  --  the  trip-rope  is  used,  but  this 
necessitates  the  handling  of  the  bucket,  and  also  involves  some 
danger,  both  to  the  top-man  and  to  the  miners  below,  in  replacing 
the  bucket  on  the  skids.  We  have  seen  queer  and  ponderous 
arrangements  hanging  in  the  head-frame  into  which  the  bucket 
was  pulled  by  the  hoisting  engineer,  when  a  construction  of  steel 
bands  and  levers  would  automatically  close  upon  the  bucket  and 
cause  it  to  be  overturned.  At  other  places  we  have  observed 
an  ingenious  contrivance  which  clutched  the  upper  chime  of  the 
bucket  and  caused  it  to  overturn  when  the  bucket  was  pulled 
higher  by  the  engine;  but  of  all  the  numerous  devices  introduced 
for  this  purpose,  we  believe  that  here  illustrated  is  the  simplest 
and  the  best  for  all-round  work.  The  design  is  furnished  by 
Mr.  Frank  Robbins,  E.M.,  of  Los  Angeles,  California,  who  used 
it  and  found  it  to  fulfil  every  requirement.  Skips  also  are  fre- 
quently employed  in  sinking  shafts,  particularly  those  of  mod- 
erate dimensions,  and  it  will  be  observed  that  there  are  points 
of  material  difference  between  the  automatic-dumping  bucket, 
and  the  automatic-dumping  skip.  In  the  former  the  bail  is  made 
fast  to  ears  near  the  top  of  the  bucket,  while  in  the  skip  the 
side-bars  extend  entirely  down  the  side  to  or  near  the  lower  end 
of  the  skip.  The  form  of  skip  referred  to  will  be  more  fully  de- 
scribed and  illustrated  later. 

The  bucket  here  illustrated,  Figs.  28  to  34,  is  intended  to  run 


70 


TIMBERING  AND   MINING 


on  skids  set  at  any  angle  which  will  permit  the  bucket  to  slide 
downward  by  gravity.  If  the  inclination  of  the  shaft  is  too  flat 
to  admit  of  this,  due  to  friction  of  the  bucket  on  the  skids,  use  a 
skip  with  wheels.  The  several  figures  show  'the  bucket  in  i£s 
various  positions,  both  before  and  after  dumping,  and  in  the 
act  of  discharging  its  load  into  the  chute  C.  The  bucket  is  pro- 


FIG. 30 


FIG.  32 


vided  with  lugs,  as  shown  in  Figs.  28  and  29.  The  skids  are 
placed  at  such  a  distance  from  each  other  that  while  ascending 
the  shaft  the  lugs  do  not  touch  the  skids.  The  lugs,  as  will  be 
noticed,  are  considerably  below  the  center  of  the  bucket,  and 
therefore  below  its  center  of  gravity.  Fig.  30  represents  the 
bucket  either  in  ascent  or  descent,  sliding  on  the  skids,  the  lugs 
being  about  2  in.  above  the  skids.  At  the  dumping  place  the 
skids  are  channeled  out  on  the  inner  edge,  so  that  the  bucket 


BUCKET   DUMPING  71 

sinks  low  enough  for  the  lugs  to  slide  upon  the  skids.  About 
2  ft.  higher  a  notch  is  cut  in  each  of  the  skids,  into  which  the 
lugs  drop.  The  engineer  then  slowly  lowers  the  bucket,  which 
overturns  as  shown  in  Fig.  31.  When  empty,  the  engineer  again 
hoists  slowly,  the  bucket  resumes  an  upright  position,  and  is 
hoisted  far  enough  for  the  lugs  to  be  raised  out  of  their  notches 
and  to  pass  above  the  latch  attached  to  the  inside  of  the  skids, 
as  shown  in  Figs.  30  to  34.  On  lowering  again  the  lugs  slip  over 
the  notches,  as  shown  in  Fig.  33,  and  the  bucket  again  descends 
the  shaft.  In  simplicity  of  construction  and  facility  of  operation 
this  means  of  dumping  buckets  at  inclined  shafts  certainly  com- 
pares favorably  with  the  methods  previously  described  and  illus- 
trated for  handling  and  dumping  buckets  at  vertical  shafts. 

Where  skips  are  used  in  place  of  buckets  in  sinking,  in  inclined 
shafts,  the  skips  may  be  dumped  automatically  by  turning  the 
track  rails  from  the  angle  of  the  shaft  to  a  horizontal  position. 
When  the  skip  is  hoisted  from  the  depths  of  the  mine,  upon  the 
forward  wheels  reaching  the  point  where  the  track  changes  from 
an  inclined  to  a  horizontal  direction,  the  forward  wheels  run  out 
on  the  horizontal  track,  while  the  continued  winding  of  the  engine 
causes  the  lower  wheels  of  the  skip  to  be  lifted  from  the  track 
by  the  draw-bar,  and  the  rock  in  the  skip  rushes  out  into  the 
bin  beneath.  To  accomplish  this  safely,  a  bumper  must  be 
placed  on  the  horizontal  track  at  the  proper  place  (to  be  deter- 
mined by  experiment,  its  position  varying  with  the  length  of  the 
skip),  against  which  the  forward  wheels  will  stop  when  hoisting. 
If  desired,  two  or  more  dumping  places  may  be  provided,  one 
above  the  other,  the  lower  one  being  for  a  water  dump,  the  upper 
one  for  ore  and  waste.  When  the  skip  is  hoisting  water  a  portion 
of  the  track  is  thrown  back  at  the  level  of  the  water  dump,  and 
the  skip  will  enter  at  that  point  and  discharge  the  water.  When 
ready  to  hoist  roclc,  the  sectional  track,  which  is  carried  on  hinges, 
is  closed,  and  the  skip,  passing  over  these  adjustable  sections, 
dumps  in  the  rock  bin  above. 

At  many  inclined  shafts  the  skips  are  provided  with  extension 
wheels  on  the  rear  axle,  these  wheels  running  on  rails  at  the  side 
of  the  main  rails.  This  arrangement  permits  the  forward  wheels 
to  follow  over  the  curved  portion  of  the  track  from  the  incline 
to  the  Jiorizcfntal,  the  rear  wheels  taking  the  wider-gage  exten- 
sion track.  The  only  advantage  in  this  is  that  in  lowering  the 


72  TIMBERING  AND   MINING 

skip  after  dumping  there  is  no  danger  of  the  rear  skip  wheels 
striking  the  track  a  heavy  blow.  This  a  careful  engineer  can 
easily  avoid  where  there  are  no  extension  rails,  as  we  have  seen 
more  than  a  thousand  times. 

Where  the  angle  of  inclination  of  the  shaft  is  very  steep  — 
approaching  90°  —  it  is  not  uncommon  to  see  the  skip  provided 
with  a  small  wheel  at  one  side,  which  engages  a  curved  groove, 
the  function  of  which  is  to  guide  the  skip  and  to  hold  it  steadily 
while  dumping,  and  later  in  lowering  again  to  position.  Such 
shafts  are  usually  provided  with  guides.  (See  Fig.  62.) 

At  vertical  shafts  dumping  devices  of  the  character  last  de- 
scribed are  in  common  use  and  have  been  found  to  operate  satis- 
factorily. At  such  places  the  groove  should  be  used.  If  not, 
some  precaution  must  be  taken  to  prevent  overwinding,  other- 
wise a  serious  accident  may  result.  When  the  horizontal  track 
and  bumper  only  are  depended  upon  to  dump  a  skip  at  a  vertical 
shaft,  the  overwinding  of  a  few  inches  will  cause  the  forward 
wheels  of  the  skip  to  run  backward  as  the  skip  overturns,  and  a 
part  of  the  load,  at  least,  will  fall  into  the  shaft,  which  would  be 
a  serious  matter  to  men  below. 


CHAPTER  IX 

» 

FRAMING   SHAFT  TIMBERS 

BEFORE  proceeding  with  the  operation  of  shaft  sinking,  we 
will  go  somewhat  into  detail  in  the  matter  of  framing  shaft  tim- 
bers. On  this  subject  there  is  a  most  varied  and  widely  scattered 
literature.  It  is  not  our  purpose  to  give  space  to  descriptions 
of,  nor  to  illustrate,  unusual  methods,  but  to  present  what  are 
generally  recognized  the  world  over  as  standard  methods  of 
framing  shaft  sets,  for  both  vertical  and  inclined  shafts.  In  the 
United  States,  in  South  Africa,  and  in  Asutralia  —  wherever 
American  engineers  have  been  in  charge  —  the  rectangular  shaft 
has  been  conceded  to  be  the  best  adapted  to  all  general  purposes, 
though  occasionally  a  square  shaft  is  found.  We  have  no  par- 
ticular interest  in  the  great  circular  and  octagonal  shafts  of 
Mexico  and  China,  further  than  that  they  are  rather  remarkable 
examples  of  engineering  of  a  somewhat  primitive  sort. 

As  to  shafts  sunk  under  peculiar  and  unusual  conditions, 
such  as  are  sunk  under  great  physical  disadvantages,  special 
methods  are  employed  —  among  them  being  sinking  through 
quicksand  by  freezing  the  water-soaked  ground;  driving  metal 
sheet-piling;  sinking  in  caissons,  and  by  the  various  other  methgds 
employed  by  engineers  who  make  this  class  of  work  a  specialty. 
Fig.  35  illustrates  a  type  of  shaft-timber  frame  at  one  time  in 
much  favor  on  the  Comstock  Lode  at  Virginia  City,  Nevada. 
It  will  be  observed  that  the  corners  are  framed  so  that  the  end 
plates  do  not  rest  upon  the  wall  plates,  but  butt  up  against  them. 
The  idea  of  this  design  was  to  minimize  the  tendency  of  the  tim- 
ber to  split  under  heavy  pressure  from  the  surrounding  ground, 
and  the  attainment  of  this  object  was  still  further  promoted  by 
cutting  a  bevel  at  the  inside  corner  of  both  end  and  wall  plates, 
as  clearly  shown  in  the  sketch,  which  is  reproduced  from  Bulletin 
No.  2  of  the  State  Mining  Bureau  of  California,  and  which  was 
drawn  by  the  author  in  1893. 

73 


74 


TIMBERING  AND   MINING 


Edge  of  End  Plate 
Inside  of  Shaft 


FIG.  35.  —  Method  of  Timbering  the  Chollar,  Norcross  and  Savage  Shaft. 
Comstock  Lode,  Virginia  City,  Nevada 


FRAMING   SHAFT  TIMBERS  75 

Fig.  36  represents  the  shaft  of  the  Argonaut  mine,  at  Jackson, 
California.  This  is  an  inclined  shaft,  sunk  at  an  angle  of  63°, 
and  is  now  nearly  3,000  ft.  deep.  It  is  a  well-timbered  shaft 
and  an  excellent  example  of  the  best  type  of  inclined  shaft  in 
the  West.  The  detail  of  framing  is  plainly  shown.  It  has  been 
suggested  that  the  ends  of  the  end  plates  be  so  framed  as  to 
dispense  with  the  bevel  at  the  outer  edges,  placing  the  end  plates 
so  that  their  outside  corner  comes  flush  with  the  extreme  end 
of  the  wall  plate.  This  would,  of  course,  save  a  little  time  in 
framing,  but  the  advantage  gained,  of  holding  the  end  plates  in 
position  until  the  set  can  be  blocked  and  wedged,  would  be  lost, 
and  the  present  method  is  no  small  advantage  in  placing  the 
timbers  of  the  set  in  position;  therefore  we  can  see  no  advantage 
in  changing  the  style  of  framing  here  presented  for  this  class  of 
shaft.  Often  in  the  smaller  shafts,  where  comparatively  small 
timbers  are  used  —  8X8  or  8  X  10  in.  — -  the  outside  bevel  of 
the  wall  plate  splits  off  when  the  end  plates  are  put  in.  Two 
spikes  driven  into  this  part  of  the  plate  will  prevent  this  wedge- 
shaped  section  from  splitting  off. 

Fig.  37  illustrates  a  section  of  the  Alma  shaft  at  Jackson, 
California,  and  is  an  adaptation  to  vertical  shafts  of  the  "dove- 
tail" style  of  framing  employed  in  inclined  shafts.  It  has  been 
introduced  extensively  in  the  past  ten  years  in  vertical  shafts 
throughout  the  West  and  appears  to  have  fulfilled  every  require- 
ment where  the  ground  was  not  shifting  by  reason  of  unequal 
pressure  or  changing  direction,  and  we  are  not  at  all  sure  that 
under  such  conditions  the  overlapping  ends  would  afford  any 
greater  security,  while  we  believe  that  timbers  framed  with  the  dove- 
tail can  be  more  readily  repaired  than  those  of  the  overlap  style. 

Framing  for  Vertical  Shafts 

Having  described  two  methods  of  framing  timbers  for  vertical 
shafts,  a  third  method  of  framing  is  here  illustrated.  The  sketch, 
Fig.  38,  shows  a  shaft  of  two  compartments  designed  for  pro- 
specting purposes;  but  as  many  compartments  as  are  desired  may 
be  added,  and  the  dimensions  of  timbers  and  size  of  compart- 
ments may  be  changed  to  suit  the  requirements.  One  or  more 
compartments  may  be  added  by  simply  increasing  the  length  of 
the  wall  plates  to  the  necessary  extent  and  inserting  dividers  at 
the  proper  places. 


76 


TIMBERING   AND   MINING 


FIG.  36.  — Argonaut  Inclined  Shaft,  Jackson,  California. 


FRAMING   SHAFT  TIMBERS 


77 


There  is  a  detail  of  the  framing  of  these  timbers  which  we 
believe  to  be,  in  most  instances  if  not  in  all,  unnecessary,  and 


FIG.  37.  —  The  Alma  Vertical  Shaft,  Jackson,  California 

that  is  the  bevel  at  the  inside  corner  of  wall  and  end  plates.  It 
is  clearly  shown  in  the  drawing.  The  practice  of  framing  tim- 
bers in  this  manner  originated  on  the  Comstock,  the  idea  being 


78  TIMBERING   AND   MINING 

that  the  bevel  minimized  the  tendency  of  the  timbers  to  split 
when  exposed  to  heavy  pressure;  but  it  is  our  experience  that 
when  the  rocks  through  which  a  shaft  is  sunk,  swell,  or  from  any 
other  cause  exert  unusual  pressure  upon  the  timber  sets,  the 
tendency  of  the  timbers  to  split  and  to  crush  is  not  materially 
decreased  by  the  bevel  at  the  inside  corners  of  the  set. 

The  sketch  of  the  Chollar,  Norcross  and  Savage  shaft,  Fig.  35, 
shows  the  same  bevel  at  the  corners  as  in  Fig.  38.  It  requires 
time  and  care  to  make  these  bevels,  and  this  means  expense, 
which  in  our  opinion  is  not  justified  by  results.  There  is  just  as 
great  a  tendency  for  wall  plates  to  split  where  the  dividers  are 
inserted,  as  at  the  corners,  and  even  more,  but  no  bevel  joint 
has,  so  far  as  we  are  aware,  been  introduced  at  that  point  in  any 
shaft,  although  there  are  a  number  of  ways  in  which  dividers 
are  framed  and  inserted  in  shaft  sets.  Particular  attention  is 
called  to  the  details  of  framing  and  instructions  as  to  how  to 
proceed.  This  appears  in  the  lettering  accompanying  Fig.  38. 
It  is  very  important  that  these  directions  be  followed  carefully, 
or  the  set  will  soon  fail  to  be  uniform,  owing  to  the  very  notice- 
able discrepancy  in  dimensions  of  sticks  of  timber  and  an  equal 
difference  in  the  dimensions  at  opposite  ends  of  the  same  timbers. 
This  is  due  to  the  carelessness  of  sawyers  in  mills  where  the  tim- 
bers are  sawed  from  the  logs. 

In  the  early  history  of  mining  in  the  West,  shaft  timbers  were 
held  in  position  until  wedged  by  the  employment  of  iron  dogs  — 
bars  of  square  iron  having  their  ends  turned  out  at  right  angles, 
and  provided  with  sharp  points.  When  the  timbers  had  been 
adjusted  as  nearly  as  possible  to  their  correct  position,  the  dogs 
were  driven  into  the  plates  and  left  there  until  several  sets  had 
been  placed,  when  the  upper  set  of  dogs  was  removed  to  be  re- 
used at  the  last  set  placed  in  the  shaft.  In  some  instances  they 
were  left  in  permanently.  In  some  of  the  older  shafts  in  Cali- 
fornia that  had  been  under  water  for  years,  and  had  recently 
been  unwatered,  we  have  seen  these  interesting  relics  of  the  early 
mining  methods. 

It  is  now  many  years  since  the  use  of  iron  dogs  was  discon- 
tinued for  that  of  bolts  provided  with  a  hook  at  one  end  and  a 
thread  at  the  other.  At  first  a  set  consisted  of  one  bolt  having  a 
hook  and  another  an  eye,  but  it  was  soon  found  that  it  was  an 
advantage  for  each  bolt  to  be  made  with  a  hook,  and  all  of  the 


FRAMING   SHAFT  TIMBERS 


79 


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FIG.  38.  —  Details  of  Framing  a  Two-compartment  Shaft  Set 


80  TIMBERING  AND  MINING 

same  length.  The  bolts  were  then  interchangeable  and  could  be 
used  at  any  place  in  the  shaft  —  either  as  an  upper  or  lower  bolt 
of  a  pair.  We  have  heretofore  made  some  remarks  on  hanging- 
bolts  and  wish  here  to  repeat  and  emphasize  some  points  of  im- 
portance. Select  good  iron  and  have  the  bars  of  sufficient  size 
to  permit  the  cutting  of  a  strong,  deep  thread,  or  the  thread  may 
strip.  Forge  the  hooks  into  well-rounded  shape,  so  that  when 
two  hooks  are  joined  the  point  of  tension  will  fall  in  line  with  the 
rods.  Avoid  burning  the  iron  when  in  the  forge,  else  the  hooks 
will  straighten  out  or  break. 

In  the  upper  part  of  a  shaft,  or  in  any  part  of  a  shaft  where  the 
rock  is  soft  and  affords  what  is  believed  to  be  insufficient  support 
to  the  timbers  by  wedging,  it  is  a  good  idea  to  substitute  straight 
iron  bolts  for  the  hooks  and  -to  allow  them  to  remain  in  place 
permanently.  In  hard  ground  more  than  5  or  6  full  sets  of  bolts 
are  not  in  use  at  one  time,  though  it  is  wise  to  have  two  or  more 
extra  sets  ready  in  the  shop  in  case  of  an  emergency,  such  as  the 
breaking  of  a  set,  or  the  mislaying  of  a  hook  or  two.  When  the 
threads  become  worn  the  end  may  be  cut  off,  a  new  piece  of  iron 
welded  on  and  a  new  thread  cut.  We  repeat  the  caution  con- 
cerning washers.  Always  use  washers  of  large  dimensions  and 
sufficiently  thick  to  prevent  breaking,  which  not  infrequently 
occurs  with  thin  washers.  The  usual  form  of  square  or  hex- 
agonal nut  is  used,  and  at  some  mines  the  nuts  are  provided  with 
handles  to  facilitate  screwing  up.  By  means  of  these  much 
time  may  be  saved.  .  .  -  _ 

The  real  function  of  hanging-bolts  is  to  temporarily  suspend 
the  timbers  in  the  shaft  safely  while  all  members  of  the  set  are 
being  put  in  place,  the  posts  inserted,  and  everything  arranged 
in  position.  The  nuts  are  then  screwed  up  tightly,  drawing  the 
timbers  into  rigid  position,  when  the  set  is  wedged  into  line. 
They  are  for  temporary  use  in  most  cases  and  are  removed  to 
be  re-used  lower  down  as  the  work  of  timbering  progresses. 
Permanent  bolts  need  be  threaded  at  one  end  only,  the  lower 
end  being  provided  with  an  "upset"  head  and  a  washer,  as  the 
adjusting  is  usually  done  at  the  upper  end. 

The  Divider  and  Spliced  Wall  Plate 

The  dividers  or  centers  placed  in  shaft  sets  for  the  purpose  of 
dividing  the  shafts  into  two  or  more  compartments  are  variously 


FRAMING   SHAFT  TIMBERS 


81 


framed.  Ordinarily  the  piece  of  timber  is  sawed  to  a  length 
equaling  the  distance  between  wall  plates,  plus  the  length  of 
the  dovetailed  or  beveled  tenon  at  each  end.  This  latter  may 
vary  somewhat  in  different  shafts,  depending  upon  the  size  of 
the  timbers  of  the  set,  a  12-in.  or  14-in.  plate  usually  being  cut 
to  a  depth  of  1{  to  1J  in.  to  receive  the  tenon  of  the  divider, 
while  in  an  8-in.  or  10-in.  timber  the  mortice  and  tenon  are  gen- 
erally but  1  in.  The  tenons  at  the  ends  of  the  divider  are  always 
beveled,  sometimes  on  both  sides,  as  indicated  by  the  dotted 
lines  in  Fig.  35,  but  more  commonly  one  side  only  is  beveled, 
the  other  being  square,  as  shown  in  Fig.  38,  in  details  of  framing. 
In  no  case  is  the  tenon  flush  with  the  side  of  the  divider,  the 


FIG.  39 

object  being  to  have  the  shoulders  protect  the  wall  plate  as  far 
as  possible  and  to  lessen  the  constant  likelihood  of  its  splitting 
under  pressure. 

Dividers  should  be  heavy  enough  to  perform  the  function  for 
which  they  are  intended  —  that  of  resisting  side  pressure  upon 
the  wall  plates,  and  to  carry  guides  and  pipes  in  the  shaft.  It  is 
customary,  however,  to  provide  for  this  purpose  timbers  which 
shall  be  equal  to  the  inner  face  of  the  wall  plate,  but  of  less  thick- 
ness. Thus  a  wall  plate  in  a  large  shaft  in  heavy  ground  may 
be  12  X  14  in.  The  14-in.  face  will  be  placed  uppermost.  The 
divider  will  then  be  12  in.  deep,  but  it  may  be  only  10  or  even 
8  in.  wide.  In  some  shafts  the  dividers  are  square.  As  there  is 
always  a  probability  of  dividers  in  the  lower  sets  being  knocked 


82 


TIMBERING  AND   MINING 


out  of  place  by  rocks  flying  from  blasts,  some  miners  cut  the 
dividers  with  the  tenon  longer  at  the  top  than  at  the  bottom, 
as  shown  in  Fig.  39.  As  the  "  horn "  projects  further  beneath 
the  post,  of  course  the  danger  of  the  divider  being  knocked  out 
by  blasting  is  lessened.  Where  there  is  heavy  side  pressure  it 
is.  good  practice  to  increase  the  height  or  depth  of  the  divider,  so 
that  it  projects  an  inch  above  and  an  inch  below  the  surface  of 
the  wall  plate,  as  shown  in  Fig  40,  which  prevents  the  center 
posts  from  being  pushed  out  of  place.  This  figure  also  shows  a 


FIG.  40 

guide  in  place,  with  what  is  known  as  a  "distance  piece"  at  the 
back  of  the  guide,  between  it  and  the  divider.  The  purpose  of 
the  distance  piece  is  to  enable  the  shaft  men  at  all  times  to  keep 
the  guides  in  perfect  alinement  (within  reasonable  limitations) 
should  the  main  members  of  the  set  be  forced  from  their  original 
position  by  unequal  pressure.  In  heavy  ground,  where  timbers 
frequently  shift  somewhat,  the  distance  piece  will  be  found  par- 
ticularly useful,  as  the  guides  can  be  kept  in  alinement  without 
the  necessity  of  shifting  the  main  timbers  until  it  becomes  posi- 
tively necessary. 


FRAMING   SHAFT  TIMBERS 


83 


Another  idea  in  the  matter  of  dividers  is  shown  in  Fig.  41. 
This  scheme  originated  in  Montana.  The  purpose  is  to  make  it 
possible  to  carry  the  main  sets  well  toward  the  bottom  of  the 
shaft  while  leaving  the  dividers  out  of  the  last  two  or  three  sets 
so  as  to  permit  the  swinging  of  long  wall  plates  into  position,  and 
also  to  lessen  the  danger  of  having  dividers  knocked  out  by 
blasts.  The  square  notch  cut  in  the  post  at  B  permits  the  divider 


FIG.  41 

to  be  slipped  in  sideways  and  then  driven  down  to  position,  after 
which  the  notch  at  B  is  filled  with  a  piece  of  plank  which  is 
secured  by  two  or  three  small  spikes,  as  at  A.  This  scheme, 
although  a  convenient  one,  is  not  in  general  use,  probably  because 
miners  believe  the  cut  at  A  weakens  the  post;  but  as  posts  are 
only  intended  to  afford  stiffness  to  the  set  and  to  keep  wall  plates 
at  the  proper  vertical  distance  from  each  other,  it  seems  that  the 


84 


TIMBERING   AND   MINING 


removal  of  a  small  section  could  work  no  great  harm.  If  the 
piece  of  plank  rots  it  can  be  removed  and  another  substituted 
in  its  place. 

Often  it  is  difficult  to  obtain  timbers  of  proper  dimensions 
that  are  sufficiently  long  for  wall  plates  in  a  large  shaft,  or  it 
may  be  desired  to  enlarge  a  shaft  by  adding  a  compartment. 
In  such  cases  the  method  of  framing  shown  in  Fig.  42  is  a  con- 
venient and  satisfactory  way  to  meet  this  contingency.  The 
ends  of  the  wall  plate  butt  against  each  other  as  shown,  the 


FIG.  42 

divider,  provided  with  a  dap  for  the  post,  overlapping  the  spliced 
wall  plate.  This  scheme  can  also  be  resorted  to  where  the  ground 
is  so  heavy  that  dividers  cannot  be  omitted,  but  must  be  put  in 
position  at  once,  and  all  sets  placed  as  soon  as  enough  rock  has 
been  removed  to  make  room  for  them.  Manifestly  it  would  be 
impossible  to  get  a  long  wall  plate  into  position  under  such 
circumstances,  owing  to  lack  of  space  within  which  to  swing  it 
into  position.  Then  the  spliced  wall  plate  can  be  resorted  to 
and  the  timbers  carried  as  close  to  the  bottom  as  desired.  In 
such  cases  the  two  hoisting  compartments  are  included  by  a 


FRAMING  SHAFT  TIMBERS  85 

single  piece;  the  pumping  and  manway  compartment  being 
usually  larger  than  either  of  the  others,  the  short  piece  of  the 
wall  plate  is  placed  at  that  end  of  the  shaft.  It  suggests  weak- 
ness, but  when  carefully  framed,  put  in  place  and  tightly  wedged, 
a  shaft  set  built  on  these  lines  is  as  good  as  any  other.  It  is  a 
mistake  to  think  that  shaft  sets,  or  mine  timbers  of  any  kind, 
are  improved  by  mortises  and  tenons  such  as  carpenters  com- 
monly make  in  building  houses,  bridges,  head-frames  and  other 
structures  above  ground.  In  mine  timbers  all  depends  on  cor- 
rect alinement  of  timbers  and  solid  wedging.  When  these  con- 
ditions are  met  they  cannot  be  improved  upon. 

The  Template 

The  framing  of  mine  timbers,  particularly  those  employed  in 
shafts  and  in  square-sets,  must  be  done  uniformly  and  with  care. 
Timber-framing  machines  are  now  made  that  perform  this  work 
with  expedition  and  accuracy.  Of  these  we  will  have  more  to 
say  later.  Where  shaft  timbers  are  framed  by  hand,  the  work 
may  be  greatly  expedited  by  employing  a  template,  which  may 
be  laid  on  the  timber  and  the  marks  scribed  by  the  timber  framer 
in  charge  of  the  work.  The  frame  must  be  carefully  made  from 
a  good  piece  of  clear  scantling,  the  templates  being  made  of  steel 
plates  that  are  secured  to  the  wooden  strip  by  strong  screws. 
The  use  of  the  template  tends  to  insure  uniformity  in  the  shape 
and  size  of  all  cuts,  and  also  keeps  the  distance  from  one  to  the 
other  constant,  whereas  there  is  always  possibility  of  an  error 
through  carelessness  when  each  timber  is  laid  out  with  scriber 
and  rule. 

Handling  Timbers  in  Shafts 

The  handling  of  timbers  at  the  collars  of  shafts,  and  the  lower- 
ing of  timbers  into  the  shafts,  requires  great  care  on  the  part  of 
those  at  the  surface.  The  work  must  be  done  quickly,  and 
absolute  safety  must  be  assured  to  the  men  below.  At  many 
inclined  shafts  a  timber  skip  or  car  is  provided  upon  which  long 
pieces  of  timber,  such  as  wall  plates,  long  stulls,  etc.,  may  be 
sent  down  in  safety.  If  there  is  sufficient  room  in  the  head- 
frame,  the  timber  car  may  be  attached  beneath  the  ore  skip, 
by  rope  or  chains.  It  is  good  practice  to  have  skids  so  arranged 
at  the  shaft  that  the  timber  truck  may  be  run  off  onto  the  platform 


86  TIMBERING  AND  MINING 

over  the  back  of  the  shaft,  where  it  may  be  pushed  into  the 
timber  shop  and  loaded  with  timbers,  which  are  then  securely 
lashed  on  the  truck  and  sent  to  the  collar  of  the  shaft;  the  rope 
or  chains  are  then  made  fast  in  the  ring  in  the  bottom  of  the 
skip,  and  the  timber  truck  with  its  load  hauled  across  the  shaft 
on  the  skids  until  the  wheels  rest  upon  the  main  track.  The 
skids  are  then  removed  and  the  loaded  timber  truck  and  skip 
are  lowered  into  the  mine  together. 

Where  there  is  insufficient  height  in  the  head-frame,  the  skip 
may  be  run  onto  the  water-dump,  where  it  is  secured  and,  the 
hoisting  rope  being  detached,  made  fast  to  the  draw-bar  or  rings 
of  the  timber  truck,  and  in  that  manner  it  may  be  lowered  into 
the  mine.  If  the  timbers  are  for  stopes,  or  for  any  other  part 
of  the  mine  than  the  shaft,  a  pair  of  skids  should  be  provided  at 
the  stations  similar  to  those  on  top,  so  that  the  timber  truck 
may  be  run  off  at  the  level  where  the  timbers  are  wanted.  This 
will  greatly  lessen  the  danger  to  men  who  may  be  below,  if  the 
timbers  are  hoisted  onto  the  level  from  the  timber  trucks  by 
means  of  snatch-blocks  suspended  from  the  roof  of  the  station. 
This  danger  is  increased  where  the  timbers  are  placed  in  skips 
or  buckets,  owing  to  the  difficulty  in  removing  them. 

At  vertical  shafts  the  timber  trolley  cannot  be  used  to  advan- 
tage. Where  cages  are  in  use,  however,  timbers  are  generally 
stood  on  end  and  lashed  to  the  frame  of  the  cage.  Long  timbers, 
such  as  wall  plates,  project  above  the  top  of  the  cage,  the  steel 
hood  being  temporarily  thrown  back  for  this  purpose.  At  most 
vertical  shafts  skips  have  replaced  cages,  though  skips  are  not 
nearly  as  convenient  as  the  latter  for  handling  timbers;  therefore 
with  skips  another  means  must  be  provided  for  the  expeditious 
and  safe  handling  of  timbers.  We  have  seen  thousands  of  tim- 
bers 24  to  30  in.  in  diameter  and  8  ft.  in  length,  besides  many  of 
smaller  dimensions,  lowered  beneath  skips  by  means  of  chains 
and  dogs.  One  of  the  mines  where  this  method  was  followed 
was  the  Utica,  at  Angels,  in  Calaveras  County,  California.  The 
stopes  in  that  mine  were  large  and  the  square-set  system  of  tim- 
bering was  employed  almost  exclusively;  the  timbers  were  mostly 
of  the  dimensions  above  given.  These  were  delivered  at  the 
collar  of  the  shaft  ready  framed  from  the  machines.  Only  one 
timber  at  a  time  could  be  sent  down  beneath  the  skip.  A  dozen 
strong  chains,  each  about  8  ft.  in  length,  were  provided.  At  the 


FRAMING   SHAFT  TIMBERS 


87 


center  of  each  chain  was  a  ring  4  in.  in  diameter,  and  each  end  of 
the  chain  terminated  in  a  strong,  sharp  dog,  forged  at  an  angle 
of  about  70°.  One  of  the  dogs  was  driven  into  one  side  of  a 
timber  somewhat  above  its  center,  the  chain  being  passed  over 
the  end,  and  the  other  dog  driven  into  the  opposite  side.  These 
dogs  were  driven  well  into  the  timber  by  means  of  sledges.  They 
had  to  be  absolutely  secure,  or  a  serious  accident  was  likely  to 
result. 


FIG.  43 

In  addition  to  the  chains  with  dogs,  a  number  of  ropes  7  or 
8  ft.  in  length,  each  provided  with  a  sharp  spike  8  in.  long,  were 
always  on  hand.  The  spike  of  one  of  these  was  driven  into  the 
lower  end  of  the  timber,  and  the  stick  was  then  ready  to  be  low- 
ered into  the  mine.  When  the  skip  came  from  below  it  discharged 
its  load,  and  was  then  lowered  to  within  about  5  ft.  of  the  collar 
of  the  shaft.  Beneath  the  skip  was  suspended  two  stout  chains 
with  rings.  A  short  piece  of  chain  having  a  strong  hook  at  each 
end  was  at  hand.  One  of  the  hooks  was  inserted  into  the  rings 


88  TIMBERING  AND  MINING 

at  the  ends  of  the  chains  hanging  beneath  the  skip,  the  other 
end  was  caught  into  the  ring  at  the  center  of  the  chain  attached 
by  the  dogs  to  the  timber.  The  signal  being  given,  the  engineer 
hoisted  slowly,  the  timber  being  lifted  and  dragged  toward  the 
shaft,  finally  clearing  the  platform  and  swinging  over  the  shaft. 
The  top-man  held  the  rope  attached  to  the  lower  end  of  the  tim- 
ber by  the  spike,  and  by  means  of  it  brought  the  timber  to  a 
position  of  rest.  The  engineer  then  lowered  the  timber  rapidly 
to  the  level  at  which  it  was  to  be  removed.  There  the  station 
tender  pulled  the  hanging  rope  over  to  him,  and  with  the  help 
of  several  men  landed  the  log  on  the  station  platform  as  the  skip 
was  lowered  by  signal.  It  looks  like  a  tedious,  expensive  and 
cumbersome  method  of  handling  timbers,  but  with  a  crew  of 
men  accustomed  to  the  work  the  timbers  were  handled  with 
surprising  rapidity,  and  I  never  knew  of  an  accident  occurring 
at  the  Utica  mine  due  to  a  timber  getting  away  while  being 
lowered  in  the  manner  described. 

A  better  method  of  lowering  timbers  is  by  means  of  a  device 
—  better  because  it  is  more  secure  and  more  expeditious.  Fig. 
43  shows  how  timbers  may  be  lowered  in  a  vertical  shaft  beneath 
skip,  cage  or  bucket  with  safety.  It  is  a  method  particularly 
adapted  to  wall  plates  of  shafts,  as  these  have  holes  bored  to 
receive  the  hanging-bolts,  but  if  an  auger  operated  by  power  be 
provided  in  the  timber  shed,  a  hole  may  be  quickly  bored  in 
every  large  piece  of  timber  going  into  the  mine,  which  will  make 
the  attachment  of  the  device  a  simple  matter. 

Some  Useful  Knots 

The  handling  of  timbers  about  shafts  necessitates  the  almost 
constant  use  of  ropes,  and  we  here  illustrate  the  timber  hitch 
(Fig.  44);  the  timber  hitch  and  half-hitch  combined  (Fig.  45), 
and  the  bowline  (Fig.  46).  These  three  are  the  most  commonly 
used  by  miners,  and  a  knowledge  of  how  to  employ  them  will  be 
found  of  great  service.  In  making  the  timber  hitch  the  rope 
is  thrown  around  the  timber  and  the  loose  end  passed  around 
the  rope  and  over  the  loop,  being  merely  wound  two  or  three 
times  around  itself.  The  engraving  shows  the  manner  of  making 
this  hitch  better  than  it  can  be  described.  Be  sure  to  pass  the 
end  of  the  rope  over  and  not  under  the  loop.  This  is  a  very 
convenient  hitch  and  suitable  for  lowering  or  hoisting  timbers 


FRAMING   SHAFT  TIMBERS 


a  short  distance,  but  we  would  not  advise  its  use  in  letting  large 
timbers  down  a  shaft,  as  sometimes  timbers  slip  in  the  timber 
hitch,  particularly  round  sticks,  and  this  tendency  is  greatly 
increased  if  the  timbers  are  wet.  For  greater  security  a  half- 
hitch  may  be  added  as  shown  in  Fig.  45.  This  takes  a  double 
hold  upon  the  timber  'and  rarely  slips.  The  half-hitch  should 
be  at  least  three  times  the  diameter  of  the  timber  from  the  tim- 
ber hitch,  as  this  further  decreases  the  likelihood  of  the  rope's 
slipping. 

The  bowline  is  probably  the  most  useful  knot  known  to  miners, 
and  is  borrowed  from  the  sailors.     It  was  doubtless  introduced 


FIG.  44 


FIG.  45 


FIG.  46 


into  mining  practice  by  Cornish  miners  many  years  since,  as  a 
great  many  of  them  are  as  able  seamen  as  they  are  miners.  It 
is  difficult  to  describe  the  method  of  making  the  bowline,  but  the 
engraving  shows  it  so  plainly  that  no  further  instruction  should 
be  required.  Take  a  piece  of  rope  and  practice  throwing  the 
bowline.  It  is  a  trick  that  can  be  quickly  acquired  and  will  be 
found  useful  a  thousand  times.  It  is  a  knot,  quickly  made, 
never  slips  when  properly  made,  and  is  easily  untied.  These 
three  knots  will  be  found  most  useful  in  handling  timbers,  and 
are  more  employed  about  vertical  than  about  inclined  shafts. 

Placing  Timbers  of  Shaft  Sets  in  Position 

Considerable  space  has  been  devoted  to  the  framing  of  shaft 
timbers,  for  both  inclined  and  vertical  shafts,   and  something 


90  TIMBERING  AND  MINING 

has  been  said  about  the  means  employed  in  lowering  heavy 
timbers  in  shafts,  whether  these  are  to  be  used  at  the  bottom 
of  a  shaft  in  process  of  sinking,  in  repairing  the  shaft,  or  to  be 
taken  off  at  one  of  the  levels  for  use  in  a  stope  or  elsewhere.  A 
great  deal  more  could  be  said,  pqrhaps,  concerning  the  framing 
of  shaft  timbers,  but  such  remarks  would  necessarily  be  confined 
to  shafts  of  special  size  and  appointments.  Such  shafts  are 
usually  sunk  under  the  direction  of  an  engineer  who  has  planned 
the  shaft  and  provided  all  of  the  special  arrangements  for  that 
particular  equipment.  However,  it  is  our  purpose  to  present 
one  or  two  more  designs  in  vertical  shafts  showing  particular 
appointments  that  have  been  suggested  by  necessity  and  expe- 
rience and  have  been  found  of  great  value  in  the  operation  of 
mines.  We  will  also  describe  and  illustrate  the  timbering  of  a 
shaft  where  the  ground  is  so  loose  or  soft  as  to  necessitate  the 
driving  of  lagging  as  the  work  proceeds.  This  is  done  in  much 
the  same  manner  as  where  lagging  is  driven  in  drifts,  the  prin- 
ciple being  identical. 

Before  proceeding  with  these,  however,  the  manner  of  putting 
the  timber  in  place  in  the  shaft  when  it  reaches  the  timber  gang 
below  will  be  described.  Ordinarily  the  timber  sets  are  carried 
well  toward  the  bottom  of  the  shaft  as  the  work  of  blasting  pro- 
ceeds, and  in  some  cases  it  is  imperative  to  keep  the  timber  well 
down  to  the  bottom  to  avert  serious  caves.  This  is  sometimes 
the  case  where  no  f orepoling  is  necessary,  but  wherever  possible 
it  is  better  to  carry  the  work  of  blasting  well  in  advance  of  tim- 
bering, for  several  reasons,  among  them  being  the  freedom  from 
damage  to  timbers  from  flying  rocks,  and  the  fact  that  drilling 
may  proceed  below  while  the  timber  gang  is  at  work  above, 
thus  saving  much  time,  which  is  often  an  important  matter. 
In  the  shafts  of  the  Rand,  South  Africa,  it  it  not  at  all  uncommon 
for  the  bottom  of  the  shaft  to  be  from  100  to  150  ft.  in  advance 
of  the  timbering,  the  skip  or  bucket  being  held  in  position  below 
the  timbers  by  a  cross-head  running  in  wire-rope  guides.  When 
the  bottom  of  the  shaft  is  so  far  below  the  last  set  of  timbers 
that  men  cannot  place  the  timbers  while  standing  on  the  bottom 
of  the  shaft,  the  first  thing  to  be  done  is  to  place  two  or  more 
stulls  (depending  on  the  size  of  the  shaft)  across  the  opening. 
These  must  be  placed  with  great  care,  and  should  preferably  be 
set  in  hitches  cut  in  the  rock  and  then  tightly  wedged.  Much 


FRAMING  SHAFT  TIMBERS  91 

depends  on  the  absolute  security  of  these  stulls,  upon  which  a 
platform  of  planks  is  to  be  laid,  for  not  only  must  it  sustain  the 
weight  of  planks  and  several  men,  but  also,  possibly,  a  ton  or 
more  of  timbers,  tools,  etc.,  before  the  set  is  in  place.  On  the 
security  of  this  platform  depend  the  lives  of  the  timbermen,  and 
of  the  men  at  work  below,  should  there  be  any.  The  platform 
must  be  made  tight  in  case  men  are  below,  so  that  no  tools, 
blocks,  or  even  the  wedges  can  fall  through.  When  the  platform 
is  in  place  —  usually  about  7  ft.  below  the  last  set,  the  first  wall 
plate  is  lowered,  as  previously  explained,  the  last  two  or  three 
dividers  having  been  omitted  from  the  sets  above  in  order  to 
permit  space  to  handle  the  long  wall  plates  when  they  arrive 
from  the  surface.  As  the  heavy  timber  comes  within  reach  of 
the  men  the  lower  end  is  carried  toward  one  end  of  the  shaft, 
and  as  it  descends  it  finally  is  laid  flat  on  the  platform.  The 
engineer  stops  the  skip  or  bucket  upon  signal.  The  rope,  or 
device,  is  detached,  and  a  rope  passed  around  the  wall  plate  and 
made  fast  by  means  of  a  securely  arranged  timber  hitch.  The 
upper  hanging-bolts  have  already  been  put  in  place  in  the  lowest 
plates  of  the  set  above.  The  hooks  are  now  placed  in  the  wall 
plate  about  to  be  hung  up.  A  glance  at  the  framing  will  show 
to  which  side  of  the  shaft  the  plate  is  to  go.  Generally  it  is  under- 
stood with  the  top-man  which  plate  is  to  be  sent  down  first. 
This  prearrangement  may  obviate  the  necessity  of  turning  a 
plate  end  for  end  and  dispense  with  much  profanity.  The  rope 
is  now  made  fast  to  the  ring  in  the  bottom  of  the  bucket  by 
means  of  the  bowline.  All  being  in  readiness,  the  signal  is  given 
the  engineer  to  hoist  slowly  —  generally  3  —  1.  He  knows  what 
is  going  on  below  from  experience  and  slowly  starts  the  engine. 
In  a  moment  the  rope  is  taut  and  the  wall  plate  is  lifted  and  is 
nearly  balanced.  The  men  guide  it  and  push  it  gently  to  the 
side  until  the  hooks  in  the  new  plate  can  be  engaged  in  those 
hanging  from  that  above.  When  this  is  accomplished,  the  signal 
is  given  to  stop  hoisting  —  1  bell.  The  engineer  then  lowers  on 
two  bells;  the  rope  is  detached  from  the  timber  and  the  bucket 
rung  up.  The  second  wall  plate  is  sent  down  and  placed  on  the 
opposite  side  of  the  shaft  in  exactly  the  same  manner.  The 
ends  may  then  be  sent  down,  or  may  already  have  been  sent 
down,  together  with  the  posts.  These  are  placed  on  the  plat- 
form. 


92  TIMBERING  AND  MINING 

If  the  shaft  set  be  framed  with  the  dovetail,  it  will  be  found 
convenient  to  have  a  gage  to  place  between  the  wall  plates  to 
adjust  them  exactly  to  the  necessary  distance  apart.  This  dis- 
tance is  determined  at  each  end  and  the  plates  held  in  position 
temporarily  by  spiking  a  piece  of  lagging  to  the  top,  using  small 
spikes.  This  is  done  at  each  end.  The  end  plates  are  then 
dropped  into  position,  the  bevel  keeping  them  from  falling 
through,  and  the  spiked  lagging  preventing  the  wall  plates  from 
spreading. 

The  posts  are  now  placed  on  the  corners  and  in  the  proper 
daps  along  the  sides.  In  some  shafts  posts  (studdles)  are  used 
only  at  the  corners,  but  if  great  rigidity  is  desired,  posts  must 
also  be  placed  opposite  each  divider.  When  the  posts  are  in 
position  the  hanging-bolts  are  screwed  up  tightly,  and  if  the  daps 
are  cut  to  the  proper  depth  and  the  posts  are  of  uniform  length 
(as  they  should  be  for  every  set)  the  timbers  will  come  into  exact 
position  and  the  plates  will  be  level.  This  must  be  constantly 
watched  in  all  shafts,  whether  inclined  or  vertical.  Should  the 
plates  get  out  of  level  from  pressure  or  other  causes,  they  must 
be  brought  back  to  level  within  a  few  sets,  without  in  the  least 
disturbing  the  alinement  of  the  shaft.  The  writer  knows  of  an 
inclined  shaft  which,  through  careless  framing  and  wedging,  got 
out  of  level.  The  foreman  undertook  to  remedy  the  difficulty 
by  cutting  the  posts  short  on  one  side  for  three  sets.  He  neg- 
lected the  alinement  and  in  the  next  200  ft.  the  shaft  had  taken 
a  "twist,"  so  that  in  that  distance  it  traveled  north  from  the  cor- 
rect alinement  nearly  13  ft.,  and  was  twisted  around  so  that  had 
it  continued  1000  ft.  further  in  the  same  way  it  would  have 
resembled  a  gigantic  corkscrew.  This  was  about  as  bad  a  job  as 
we  have  ever  seen,  but  even  an  Italian  foreman  should  have 
sense  enough  to  keep  the  hoisting  rope  in  the  middle  of  the  track, 
though  this  particular  one  seemingly  did  not. 

If  the  overlap  framing  is  in  use  the  end  plates  may  be  laid 
upon  the  ends  of  the  wall  plates  and  the  temporary  binders  may 
be  dispensed  with  by  immediately  placing  blocks  at  the  corners 
and  wedging  the  set  up  firmly  but  not  too  tightly,  for  the  shaft 
has  yet  to  be  lined  up  accurately.  When  the  posts  have  all  been 
placed,  whether  in  vertical  or  inclined  shaft,  the  set  should  be 
blocked  and  wedged  to  the  rocks  surrounding  the  shaft. 


FRAMING  SHAFT  TIMBERS  93 

Placing  Timbers  in  Inclined  Shafts  and  Lining  the  Sets 

The  placing  of  timbers  in  inclined  shafts  is  attended  with 
more  difficulty  than  in  performing  the  same  work  in  vertical 
shafts.  If  the  angle  of  inclination  is  less  than  70°,  and  the  timbers 
large  in  size,  much  lifting  is  necessary.  In  general  practice  the 
timbering  is  kept  well  down  toward  the  bottom  as  work  of  sinking 
advances.  This  is  in  part  due  to  the  increased  difficulty  in  placing 
the  timbers  in  position,  and  in  part  to  the  greater  danger  of  the 
caving  of  the  hanging-wall  of  the  shaft. 

It  is  at  once  apparent  that  in  an  inclined  shaft,  unless  it  be 
at  an  angle  approaching  90°,  the  heavy  wall  plates  cannot  be 
put  in  position  in  the  same  manner  as  the  plates  are  placed  in 
vertical  shafts.  There  is  always  more  or  less  lifting,  and  the  men 
of  the  timber  gang  must  be  strong  and  experienced  in  the  work. 
When  a  new  set  is  to  be  placed  at  the  bottom  of  an  inclined  shaft, 
the  first  thing  to  be  done  is  to  ascertain  that  the  ground  is  clear 
of  the  outside  alinement  of  the  set  on  all  sides  —  that  there  are 
no  projecting  points  or  shoulders  which  may  later  prove  to  be 
in  the  way  and  have  to  be  beaten  or  moiled  off.  This  kind  of  work 
can  be  done  much  more  quickly  when  no  timbers  interfere  with 
the  work.  It  is  particularly  necessary  to  see  that  the  foot  side  is 
clear.  The  sill  plate  is  the  first  sent  down  from  the  surface. 
This  is  placed  in  position  with  great  care.  It  must  be  in  aline- 
ment with  the  sets  above  and  must  be  perfectly  level.  This  latter 
point  is  of  greatest  importance,  for  if  the  foot-wall  plates  get 
out  of  level  the  shaft  is  soon  in  bad  condition,  and  it  may  be 
necessary  to  do  much  expensive  work  to  bring  the  timbers  into 
exact  line.  A  mistake  in  side  alinement  would,  in  any  event, 
probably  be  so  small  as  not  to  be  quickly  noticeable,  and  may 
usually  be  corrected  by  wedging  without  much  trouble.  Even 
a  mistake  in  angle  of  inclination  is  not  so  serious,  for  if  too  high 
the  plate  can  be  cut  down  with  chisels  to  lower  the  rails  to  the 
proper  height;  or  if  too  low  the  plate  may  be  wedged  or  built  up; 
but  if  not  level,  great  difficulty  is  likely  to  be  experienced  in 
remedying  this  defect. 

The  three  things,  then,  to  be  most  carefully  observed  are  that 
the  foot-wall  plate  is  absolutely  level  —  not  higher  at  one  end 
than  at  the  other;  that  it  is  exactly  in  line  with  the  angle  of 
inclination  of  the  shaft,  unless  raised  or  lowered  intentionally, 


94  TIMBERING   AND   MINING 

where  the  angle  of  inclination  of  the  shaft  is  to  be  changed;  and 
to  further  see  that  the  direct  alinement  of  the  shaft  is  main- 
tained. All  of  these  things  can  best  be  done  by  means  of  a  tran- 
sit, but  as  mine  foremen  are  not  all  familiar  with  the  use  of  the 
transit,  and  as  every  mine  does  not  employ  an  engineer,  other  less 
refined  methods  are  often  employed  that  give  very  satisfactory 
results. 

Among  the  tools  generally  employed  for  the  purpose  are  the 
spirit-level,  steel-square,  and  a  20-ft.  straight-edge.  The  level 
is  indispensable  in  placing  the  foot-wall  plate  in  absolute  hori- 
zontal position,  and  the  square  is  useful  in  placing  the  end-plates 
vertical  in  reference  to  the  side.  The  straight-edge  is  looked 
upon  as  an  instrument  of  precision  by  the  shaft  men,  but  it  is 
often  something  else.  It  is  subjected  to  more  or  less  abuse, 
receiving  many  a  blow,  is  exposed  to  heat  and  cold,  wet  and  dry, 
and  if  it  does  not  warp  a  little  it  is  a  wonder.  The  edges  in  time 
become  worn  unequally,  and  though  as  perfect  as  the  ingenuity 
and  skill  of  the  carpenter  can  make  it  when  new,  it  in  time, 
through  these  many  abuses,  becomes  unreliable,  and  a  slight 
error  due  to  a  defective  straight-edge  is  repeated  and  perpetuated 
until  the  shaft,  in  a  distance  of  200  ft.  or  more,  will  exhibit  a 
beautifully  true  transition  curve.  An  attempt,  too  late,  is  made 
to  correct  this,  and  an  abrupt  bend  is  made,  not  noticeable  until 
a  dozen  sets  are  in  place,  when  it  may  be  seen  plainly  enough  on 
looking  along  the  timbers,  if  there  be  light  enough  to  see  it. 

One  of  the  best  ways  to  secure  alinement  is  to  make  a  mark 
or,  better,  to  drive  a  tack  about  6  in.  from  the  inside  corner  at 
each  end  of  the  plate.-  Some  make  a  light  cut  with  a  saw,  but 
this  is  bad  practice  as  it  weakens  the  timber,  and  under  pressure 
this  weakness  is  noticeable,  for  the  timber  frequently  begins  to 
split  at  the  "saw-craft."  To  drive  a  bright  tack  —  galvanized 
tacks  are  good  —  is  a  better  scheme.  These  tacks,  in  the  center 
of  the  timber  and  6  in.  from  the- end  plate,  are  always  easy  to 
find.  Then,  when  four  or  five  sets  have  been  put  in  place  under 
the  direction  of  an  engineer  or  some  one  familiar  with  the  use 
of  the  transit,  the  work  may  proceed  by  employing  so  simple 
a  thing  as  a  tightly  drawn  chalk-line:  one  man  five  or  six  sets 
above;  one  at  the  new  set  (or  the  line  may  be  made  fast  at  the 
proper  places  by  means  of  two  nails)  and  the  foreman,  or  timber 
boss,  along  the  line,  particularly  at  the  last  completed  set.  If 


FRAMING  SHAFT  TIMBERS  95 

the  new  plate  on  the  bottom  is  not  in  alinement,  the  chalk  line, 
held  or  nailed  exactly  over  the  tack  in  the  new  plate,  and  over 
that  on  the  sixth  plate  above,  will  not  cover  the  tack  on  the 
last  completed  set.  The  new  plate  must  then  be  driven  by 
means  of  wedges  or  otherwise  to  right  or  left  until  the  lines  do 
coincide.  For  the  sake  of  greater  exactness,  and  proof,  the  line 
should  be  tried  on  the  tacks  at  the  opposite  end.  The  spirit- 
level  will,  if  employed  with  care,  be  sufficient  in  securing  the  plate 
in  horizontal  position.  When  the  foot-wall  plate  has  been  placed 
and  wedged  at  the  ends  so  that  it  cannot  shift,  the  hanging-bolts 
should  be  put  in,  and  the  studdles,  or  posts,  set  in  their  respec- 
tive daps  and  the  bolts  screwed  up. 

The  men  are  now  ready  for  the  hanging-wall  plate.  This 
comes  down  with  the  galvanized  tacks  driven  on  the  inner  side 
at  exactly  the  same  distance  from  the  corners  as  in  the  foot-wall 
plate.  When  ends  and  all  the  posts  are  at  the  bottom  of  the 
shaft,  the  timbers  are  distributed  so  as  to  have  them  handy.  If 
not  too  heavy  the  men  lift  the  hanging-wall  plate  and  the  ends 
are  slipped  in  from  above;  the  upper  studdles  are  placed  in  posi- 
tion and  held  there,  while  men  adjust  the  hanging-bolts  of  the 
upper  plate  and  screw  them  up  as  quickly  as  possible.  The  set 
is  then  wedged  temporarily,  and  preparations  made  to  proceed 
with  the  alinement. 

If  the  wall  plates  are  long  and  very  heavy,  the  labor  may  be 
lightened  somewhat  by  first  placing  two  skids  reaching  from  the 
foot  wall  of  the  shaft  upward  to  the  rock  face  and  below  the  posi- 
tion to  be  occupied  by  the  plate.  The  plate  is  then  sent  down 
and  is  laid  across  the  skids,  when  it  may  be  rolled  or  slid  upward 
on  the  skids  to  a  position  approximating  the  one  it  is  to  occupy 
permanently.  The  ends  may  then  be  slipped  in,  the  hanging- 
bolts  inserted,  and  the  posts  placed,  when  the  bolts  may  be 
tightened.  When  the  set  is  in  pla*ce  the  skids  may  be  removed, 
they  having  served  their  purpose.  Blocking  is  then  put  back  of 
the  timbers  at  the  corners,  or  wherever  necessary,  and  wedged, 
but  not  too  tightly. 

The  foot-wall  plate  being  in  absolutely  exact  position  the 
hanging-wall  plate  must  now  be  brought  into  line.  Chalk  lines 
are  made  fast  on  the  new  hanging-wall  plate,  and  at  the  seventh 
hanging-wall  plate  above,  and  the  lines  are  also  replaced  on  the 
foot-wall  plates.  Plumb-bobs  with  short  lines  are  attached  to 


96  TIMBERING  AND  MINING 

the  upper  lines  at  a  point  vertically  above  the  set  number  2 
(calling  the  new  set  number  1).  The  plummets  should  be  of  the 
long  kind  terminating  in  a  sharp  point.  This  point  should  hang 
directly  over  the  lower  line,  for  if  it  does  not  the  ends  are  not  in 
exact  position  and  the  hanging-wall  plate  must  be  shifted  by 
easing  and  wedging  until  correct  adjustment  is  secured.  This 
may  also  be  done  by  means  of  the  spirit-level  held  upright,  but 
there  is  more  likelihood  of  error  resulting  from  inequalities  of 
the  timber  and  short  distance  than  by  means  of  the  lines  and 
plumb-bobs. 

Difficulties  in  Sinking  Through  Running  Ground 

Sometimes  shafts  in  sinking  must  pass  through  soft,  water- 
soaked  rock.  Whenever  this  occurs,  no  matter  what  the  kind 
of  rock,  whether  the  muck  of  a  slaty  gouge,  the  soft  unctious 
talcose  material  of  talc-schist  or  crushed  serpentine,  or  whether 
it  be  "  rotten  "  granite  or  crumbling  sandstone,  there  is  trouble  in 
store  for  the  miner,  and  often  danger  as  well.  Decomposed 
sandstone  and  limestone  will  sometimes  run  like  sand  when  dry, 
and  this  tendency  is  increased  to  a  dangerous  degree  when  the 
country  is  wet.  The  experience  at  the  Alpha  shaft  of  the  Giroux 
Consolidated  mine,  at  Ely,  Nevada,  in  1908,  was  an  example 
of  the  dangers  of  sinking  through  loose  material.  A  run  started 
in  that  shaft  at  some  unprotected  place,  and  this  loosened  some 
of  the  blocking,  which  permitted  the  lagging  of  a  set  to  drop  out, 
and  the  shaft  simply  collapsed  for  hundreds  of  feet,  as  the  soft 
disintegrated  material  shifted,  loosening  the  blocking.  It  cost 
the  lives  of  two  men  and  many  thousands  of  dollars,  and  it  is  a 
wonder  that  the  cave  was  ever  caught  up  at  all.  Great  praise 
is  due  the  men  who  heroically  worked  in  imminent  danger  for 
weeks  to  rescue  their  companions  imprisoned  below. 

Leadville,  Colorado,  has  numerous  instances  of  caving  shafts, 
caused  by  stoping  ground  too  close  to  the  shaft.  Of  these  the 
Bon  Air  shaft  is  an  example.  Hundreds  of  bales  of  hay  were 
dumped  into  that  hole  and  the  run  was  finally  checked  and  the 
shaft  recovered.  But  these  are  instances  of  caving  and  recovery 
after  the  shafts  had  been  put  down. 

There  are  many  places  where  shafts  may  be  sunk  in  safety 
through  soft  ground,  so  long  as  it  is  dry,  but  let  water  come  in 
contact  with  it  and  nothing  short  of  several  feet  of  concrete  could 


FRAMING   SHAFT  TIMBERS  97 

hold  it.  There  are  numerous  examples  of  this  sort  of  ground  in 
the  mines  of  the  Mother  Lode  of  California,  of  which  the  Amador 
Queen,  No.  1,  a  mile  and  a  half  south  of  Jackson,  in  Amador 
County,  is  a  type.  The  shaft  is  over  1200  feet  deep.  Heavy 
gouges  are  an  important  geological  characteristic  of  this  mine, 
but  it  is  dry  and  no  great  difficulty  was  experienced  in  sinking 
a  good-sized  two-compartment  shaft  at  a  cost  of  only  $30  per 
foot,  which  on  the  Mother  Lode  may  be  considered  as  indicating 
"easy  ground." 

Where  a  shaft  must  pass  through  water-soaked  running 
ground  extraordinary  precautions  must  be  taken.  Some  mining 
engineers  have  made  a  specialty  of  sinking  shafts  through  quick- 
sand and  wet,  running  ground,  and  in  some  instances  elaborate 
and  expensive  preparations  had  to  be  made  and  special  methods 
employed.  Among  these  are  the  freezing  of  the  ground  by  means 
of  pipes  driven  into  the  ground  to  be  excavated,  and  circulating 
ammonia  through  the  pipes,  operating  in  essentially  the  same 
manner  as  ice-making  machines.  This  causes  the  ground  to 
congeal  for  a  time,  when  it  may  be  excavated,  and  the  excavation 
made  secure  by  means  of  steel  sections  or  massive  timbers  sur- 
rounded by  tight  lagging.  This  process  is  exactly  the  reverse 
of  shaft  sinking  in  afaic  regions  where  the  ground  is  solidly  frozen 
and  must  be  thawed  by  means  of  pipes  filled  with  steam  under 
pressure  from  a  boiler  and  driven  into  it  as  the  ground  softens. 

Sinking  Through  Running  or  Loose  Ground 

As  previously  stated,  the  sinking  of  shafts  through  running 
ground,  or  that  which  is  loose  and  caves  readily,  is  attended  with 
both  difficulty  and  danger.  To  overcome  these  difficulties 
various  special  methods  have  been  introduced  with  greater  or 
less  success,  some  of  them  expensive  and  elaborate,  but  the  method 
most  commonly  employed  is  that  of  driving  lagging  (forepoling) 
into  the  loose  ground,  thus  forming  a  tight  box-like  dam  around 
the  outside  of  the  timber  frame,  inside  of  which  the  work  may 
progress  with  safety  and  with  greater  or  less  expedition,  depend- 
ent largely  upon  the  conditions  to  be  met,  chiefly  the  character 
of  material  to  be  removed  and  the  amount  of  water  present. 
Where  water  is  abundant  in  loose  material,  particularly  that  which 
runs  readily,  it  is  a  good  maxim  to  "  make  haste  slowly,"  for  an 
attempt  to  rush  the  work  may  meet  with  a  back-set.  It  is  much 


98  TIMBERING  AND   MINING 

better  to  go  about  it  deliberately,  giving  the  ground  time  to  drain, 
by  cutting  a  sump  hole  at  some  convenient  place  in  the  bottom 
of  the  shaft  and  removing  the  water  as  fast  as  it  comes  in,  either 
by  means  of  a  sinking-pump  or  by  bailing,  the  means  to  be  deter- 
mined by  the  amount  of  water  coming  in. 

It  is  very  necessary  to  have  first-class  timbers  and  lagging  for 
sinking  through  ground  of  this  sort,  and  while  split  spruce  lagging 
may  be  preferred  in  passing  through  dry  ground,  or  where  the 
rock  stands  fairly  well  and  will  not  run,  smooth  sawed  lagging 
is  absolutely  necessary  in  this  kind  of  ground,  because  split 
lagging  has  many  inequalities  of  surface,  and  there  is  often  con- 
siderable space  between  adjacent  pieces,  due  to  these  inequalities. 
The  sawed  lagging  must  be  placed  close  together  and  the  swelling 
of  the  wood  due  to  the  water  will  cause  all  inequalities  to  close, 
and  if  properly  placed  and  sufficiently  strong  they  will  permit 
sinking  through  very  bad  loose  and  running  ground. 

When  sufficient  progress  has  been  made  in  the  shaft  to  admit 
of  placing  an  additional  set  of  timbers,  the  main  members  of  the 
set  —7  wall  and  end  plates,  posts,  dividers,  etc.  —  are  placed  in 
position  in  the  manner  already  explained  in  former  chapters. 
There  is  this  important  difference,  however.  In  the  sets  now 
under  contemplation  a  "  bridge  "  is  used.  This  is  a  piece  of  timber 
of  a  size  to  be  determined  by  the  size  of  the  shaft,  dimensions  of 
main  timbers,  and  condition  of  the  ground.  Ordinarily  timber 
4  X  10  in.  is  heavy  enough.  This  bridge  is  in  a  single  section 
at  the  ends  of  the  shaft,  but  may  be  made  in  two  or  more  sections, 
at  the  sides.  These  are  placed  outside  the  wall  and  end  plates 
parallel  with  them  and  separated  from  them  by  wedge-shaped 
blocks,  as  shown  in  Fig.  47,  where  B  is  the  bridge  and  W  the  wedge 
blocks.  The  end  of  the  lagging  is  inserted  between  the  bridge 
and  the  wall  plate  and  driven  downward  as  the  work  of  excava- 
tion progresses,  and  ahead  of  excavation,  the  ends  being  driven 
into  the  soft  ground  as  far -as  possible.  The  lagging  is  kept 
pointed  outward  by  means  of  a  block  at  C,  which  prevents  the 
upper  end  from  working  outward  as  the  lower  end  meets  the 
resistance  and  pressure  of  the  ground  below.  In  some  cases  it 
may  even  be  necessary  to  employ  the  false-set,  though  this  is  not 
of  frequent  occurrence. 

In  some  large  shafts  a  small  shaft  is  sunk  within  the  main 
shaft,  something  after  the  manner  of  digging  sewer  trenches  in 


FRAMING   SHAFT  TIMBERS 


99 


city  streets.  The  chief  object  of  this  is  to  carry  a  sump  in  advance 
which  will  relieve  the  ground  of  much  water,  rendering  it  less 
troublesome  to  cut  out  the  ground  for  the  main  shaft,  and  to 
place  the  timbers  with  as  little  delay  as  possible.  Lagging  is 
driven  on  all  four  sides  of  the  shaft,  always  as  close  as  possible, 
and  the  work  is  advanced  on  each  side  evenly  —  that  is,  one  side 
or  end  must  not  be  much  in  advance  of  any  other.  The  process 
of  sinking  shafts  under  the  con- 
ditions here  contemplated  is 
very  much  the  same  in  principle 
as  driving  lagging  in  drifting 
through  similar  ground,  and  the 
methods  of  drifting  are  applied 
to  shaft  sinking  in  essentially 
the  same  manner,  even  to  the 
carrying  of  breast-boards,  which 
has  previously  been  described 
and  illustrated. 

No  hard  and  fast  rules  can 
be  laid  down  for  work  of  this 
character.  The  workmen  must 
have  experience,  or  gain  experi- 
ence in  trying  to  do  the  work 
themselves,  and  in  timbering 
shafts  experience  is  a  most  ex- 
cellent teacher.  The  fundamen- 
tal principles  have  been  clearly 
stated,  and  the  work  or  method 
has  been  illustrated.  The  tim- 
berman  must  necessarily  have 
some  initiative  himself,  and  act 
promptly  should  anything  un- 

looked  for  occur.  The  first  thing  to  be  considered  is  safety  to 
the  men  employed;  the  next,  expedition  in  the  work,  and  this 
will  be  determined  by  conditions,  and  as  has  already  been 
said,  the  greatest  speed  is  not  always  attained  by  rushing  a  shaft 
through  soft,  water-soaked  ground. 

The  east  shaft  of  the  Kennedy  mine  at  Jackson,  California,  is 
to-day  the  deepest  vertical  shaft  in  California,  and  one  of  the  deep 
shafts  of  the  world,  being  now  more  than  3100  ft.  deep.  This 


FIG.  47 


100 


TIMBERING   AND   MINING 


FRAMING   SHAFT  TIMBERS 


101' 


shaft  is  sunk  in  hard  greenstone,  and  no  pressure  developed  nor 
need  have  been  anticipated  in  such  ground,  but  when  the  upper 
part  of  the  shaft  was  sunk  in  1900,  it  was  deemed  advisable  to 
employ  the  bridge.  Just  what  object  was  in  view  we  do  not 
know,  unless  it  was  thought  that  by  the  employment  of  this 
method  it  might  be  easier  to  keep  the  shaft  in  line,  in  case  of 
subsequent  movement  of  the  rock  walls  —  of  which  there  was 
not  the  slightest  likelihood.  Possibly  the  idea  originated  from 
the  experience  of  the  next  mine  on  the  north  —  the  Oneida, 


Wedge 


FIG    49 

where  a  vertical  shaft  was  sunk  through  hard  greenstone,  and 
which  encountered  the  vein  fissure  at  1900  ft.,  where  the  rock 
was  black  slate  on  both  walls  with  a  heavy  gouge.  The  move- 
ment of  the  rocks  in  the  vicinity  of  the  vein  afterward  caused  the 
Oneida  management  much  trouble,  and  possibly  it  was  to  avoid 
similar  difficulty  that  the  Kennedy  management  adopted  the 
bridge  early  in  the  work.  This  was  wholly  unnecessary,  for  the 
bridge  could  have  been  introduced  or  discontinued  at  any  part 
of  the  shaft,  and  moreover,  when  a  shaft  passes  out  of  hard 


102  TIMBERING  AND  MINING 

ground  into  soft,  swelling  ground  a  different  and  more  substan- 
tial method  of  proceeding  than  the  introduction  of  the  bridge 
should  be  resorted  to.  The  bridge  is  useful  in  passing  through 
running  or  very  loose  ground,  but  is  not  calculated  to  resist  the 
pressure  due  to  swelling  ground. 

The  accompanying  illustrations,  Figs.  48  and  49,  show  the  plan 
and  end  at  one  corner  of  the  Kennedy  shaft.  It  will  be  observed 
that  it  differs  materially  from  the  arrangement  shown  in  Fig.  47. 
The  bridge  in  the  Kennedy  shaft  is  without  usefulness,  and  there- 
fore an  unnecessary  expense,  which  might  have  been  omitted 
until  it  became  a  necessity.  It  will  be  noticed  by  referring  to 
the  illustrations  that  the  lagging  in  the  Kennedy  shaft  was  not 
driven,  but  placed  in  position  in  the  same  manner  as  lagging  is 
usually  placed  in  shafts  in  hard  ground. 

Combination  Vertical  and  Inclined  Shafts 

In  many  instances  it  is  necessary  to  sink  vertical  shafts  to 
reach  veins  which  lie  at  a  comparatively  low  angle,  and  not 
infrequently  it  is  advisable  to  turn  the  shaft  from  the  vertical 
direction  to  an  inclination  conforming  to  the  pitch  of  the  vein. 
This  has  been  done  at  a  number  of  deep  mines  on  the  Rand  in 
South  Africa,  on  the  Mother  Lode  of  California,  and  in  other 
places. 

In  numerous  instances  vertical  shafts  are  sunk  to  the  vein, 
and,  passing  through  it,  the  shaft  is  continued  in  a  vertical  direc- 
tion, the  vein  being  reached  by  cross-cuts,  both  above  and  below 
the  level  at  which  the  vein  is  intersected  by  the  shaft;  but  this 
practice  is,  or  should  be,  confined  to  veins  having  a  relatively 
high  angle  of  dip,  those  of  low  inclination  being  worked,  as  pre- 
viously mentioned,  through  a  combined  vertical  and  inclined 
shaft,  where,  as  on  the  Rand,  it  is  necessary  to  reach  the  vein 
through  a  vertical  shaft,  due  to  the  fact  that  the  outcrop  is  owned 
by  others. 

There  are  important  considerations  that  cannot  be  overlooked 
when  contemplating  this  change  from  vertical  to  inclined,  par- 
ticularly where  rapid  running  is  necessary  to  hoist  large  tonnage 
within  limited  time.  In  such  cases  it  is  inexpedient,  or  at  least 
undesirable,  to  slow  up  the  skip  when  running  past  the  curve,  and 
for  this  reason  the  work  must  be  directed  with  care  by  an  engineer, 
who  will  lay  out  a  transition  curve  in  such  lines  as  to  avoid  as 


FRAMING  SHAFT  TIMBERS 


103 


8"!  AND'  !16".X61  CARERS 


80'0"    RADIUS  TO  INSIDE  OF  WALL  PLATE  OR  BOTTOM  OF  RAIL 


FIG.  50 


104  TIMBERING   AND   MINING 

far  as  possible  the  shock  incident  to  a  change  of  direction  in  the 
rapidly-moving  skip. 

This  subject  has  been  well  treated  by  Thomas  H.  Leggett  in 
the  "Transactions  of  the  American  Institute  of  Mining  Engi- 
neers," vol.  XXX,  under  the  title  "Deep-level  Shafts  on  the 
Witwatersrand,"  in  which,  concerning  this  change  from  vertical 
to  inclined,  he  says:  "Most  of  the  deep-level  shafts  of  the  first 
row  have  been  turned  upon  the  incline,  and  many  of  the  shafts 
of  the  second  row  will  unquestionably  be  so  turned;  hence,  I 
have  shown  in  the  accompanying  sketch  (Fig.  50)  the  usual 
method  of  making  and  timbering  this  turn.  Its  advantages  are 
numerous.  It  avoids  the  expense  of  a  separate  underground 
hoist,  and  enables  development  on  the  reef  to  proceed  with  the 
least  possible  delay.  The  skip  runs  from  the  incline  into  the 
vertical  smoothly,  and  generally  without  any  decrease  in  speed 
whatever;  hence  it  is  probable  that  its  use  will  be  continued  in 
shafts  up  to  3000  ft.  vertical  depth.  After  that  depth,  in  all 
probability,  independent  methods  of  hoisting  on  the  incline  will 
have  to  be  adopted.  At  the  same  time,  it  is  not  at  all  certain 
that  the  use  of  the  Whiting  hoist  will  not  permit  the  turning  of 
vertical  shafts  upon  the  incline,  even  at  this  or  greater  depth." 

The  sketch  illustrates  the  manner  of  timbering  work  of  this 
description.  It  may  be  varied,  of  course,  to  suit  any  change  in 
conditions  at  various  places.  Particular  attention  is  called  to 
the  disposition  of  the  pulleys  on  the  hanging-wall  side  of  the  shaft, 
the  function  of  which  is  to  carry  the  hoisting  rope  around  the  curve 
without  unnecessary  friction  or  damage  to  the  timbers.  It  also 
shows  the  disposition  of  the  angle-iron  guide  rails  which  prevent 
the  skip  wheels  from  leaving  the  track.  It  may  be  argued  that 
an  unnecessary  amount  of  ground  has  been  removed  from  the 
foot-wall  side  of  the  curve,  but  this  is  advisable,  as  it  permits 
the  construction  of  a  timber  frame  which  makes  it  possible  to 
put  in  a  curve  that  will  remain  absolutely  rigid  under  the  stress 
of  work,  with  skips  running  at  a  high  rate  of  speed.  If  the  tim- 
bering were  not  placed  in  this  manner  a  much  lower  degree  of 
security  would  be  possible. 


CHAPTER  X 

BEARERS   IN  SHAFTS 

IT  must  be  understood  that,  while  blocking  and  wedges  are 
employed  to  hold  shaft  timbers  firmly  in  position,  that  any 
alternation  of  wet  and  dry  will  have  the  effect,  during  the  dry 
periods,  of  causing  the  timbers,  blocks  and  wedges  to  shrink, 
sometimes  to  such  an  extent  that  the  latter  become  loose  and 
drop  out;  security  is  then  at  an  end,  for  the  timber  sets  then  have 
a  tendency  to  settle  by  gravity,  and  every  little  subsidence  or 
disarrangement  is  increased  from  set  to  set  until  there  is  danger 
of  collapse  of  the  entire  structure.  To  obviate  this,  what  are 
known  as  "  bearers  "  are  introduced,  usually  at  each  50  ft.  Where 
stations  are  100  ft.  apart,  a  bearer  half  way  between  is  considered 
sufficient  to  support  the  sets  dependent  upon  it. 

The  bearers  are  heavy  timbers  extending  across  the  ends  of 
the  shaft,  resting  their  ends  in  hitches  cut  in  the  solid  rock.  The 
bearers  must  be  perfectly  level  and  are  so  placed  that  the  ends 
have  a  solid  bearing  on  the  hitch  of  at  least  6  in. ;  more  is  better. 
The  more  loose  the  rock  in  which  the  sinking  is  being  done,  the 
greater  the  necessity  for  firmly  placed  bearers.  Upon  the  bearers 
the  ends  of  the  wall  plates  rest,  the  end  plates  being  placed 
in  the  usual  manner.  No  change  need  be  made  in  the  framing 
of  the  wall  plates,  as  the  shallow  dap  cut  on  the  under  side  to 
receive  the  post  now  rests  in  a  similar  dap  cut  in  the  bearer  to 
receive  the  wall  plate.  These  daps  keep  the  wall  plate  from  shift- 
ing in  either  direction.  On  the  under  side  of  the  bearer  daps  are 
cut  to  receive  the  posts  of  the  set  beneath.  The  bearers  should 
be  at  least  as  heavy  as  the  plates,  and  greater  depth  is  advisable, 
as  the  timber  is  weakened  a  little  by  the  daps  cut  on  both  upper 
and  lower  sides. 

Where  shaft  plates  are  12  X  14  in.,  placed  with  the  broad 
side  up,  the  bearers  should  be  14  X  16  in.,  placed  with  the  14-in. 
face  up.  This  makes  the  upper  surface  conform  to  the  size  of 

105 


106  TIMBERING  AND  MINING 

the  shaft  timbers  and  affords  the  additional  strength  which  may 
be  necessary  when  the  hanging-bolts  have  been  removed,  should 
any  shrinkage  take  place  in  blocking  or  wedges,  or  should  the 
support  of  the  shaft  walls  be  weakened  from  any  other  cause. 
The  bearer  must  be  strong  enough  to  support  the  weight  of  the 
ten  sets  of  timber  resting  upon  it  —  50  ft.  of  the  usual  shaft 
timbering.  This  is  the  theoretical  requirement,  but  it  is  seldom 
reached,  for  under  almost  any  circumstances  that  can  be  con- 
ceived, it  is  difficult  to  imagine  all  support  removed  from  each 
and  every  one  of  the  ten  sets.  However,  it  is  well  to  put  in  strorlg 
bearers,  and  to  remember  that  their  usefulness  wholly  depends 
upon  their  being  set  upon  solid  rock  and  firmly  wedged.  Shaft 
construction  is  far  more  careful  and  exacting  work  even  than 
that  usually  done  in  the  erection  of  frame  buildings.  Shafts  are 
likely  to  be  subjected  to  strains  and  tension  such  as  no  building 
is  ever  required  to  sustain,  and  this  demands  that  the  timbering 
be  properly  framed  and  placed  with  precision. 

There  is  one  more  important  matter  in  relation  to  sinking 
shafts  through  ground  which  at  the  time  gives  little  unusual 
trouble,  but  which,  it  is  known  from  its  character,  will  cause  no 
end  of  trouble  later  unless  a  method  of  timbering  be  adopted  that 
will  make  it  possible  to  meet  the  conditions  that  are  expected  to 
develop.  Reference  is  here  made  to  swelling  ground,  which, 
miners  generally  will  agree,  it  is  impossible  to  hold  with  timber, 
except  where  provision  is  made  in  the  system  of  timbering  that 
will  make  it  possible  to  relieve  the  ground  as  it  gradually,  but 
irresistibly,  encroaches  upon  the  shaft. 

There  are  different  kinds  of  ground  that  swell,  among  them 
rotten  granite  (rarely),  clay,  foliated-slate,  slaty-gouge,  ser- 
pentine, and  slate  itself.  Some  of  these  swell  more  speedily  than 
others  upon  exposure  to  the  atmosphere,  but  in  the  opinion  of 
the  writer  none  of  the  various  kinds  ultimately  give  more  trouble 
than  the  slate,  which,  firm  enough  when  first  cut,  within  a  week 
or  two  shows  signs  of  crowding  the  timbers,  and  within  a  month 
begins  to  bend,  displace  and  to  break  them. 

On  the  Mother  Lode  of  California,  particularly  in  the  counties 
of  Amador  and  Calaveras,  this  kind  of  ground  is  well  known,  and 
the  experience  of  more  than  half  a  century  in  that  district  should 
have  developed  methods  of  dealing  with  the  difficulty  which 
would  be  of  value  elsewhere.  The  shafts  on  the  Mother  Lode 


BEARERS  IN   SHAFTS  107 

which  experience  this  difficulty  with  swelling  ground  are  mostly 
inclines  sunk  in  the  vein  fissure  —  sometimes  in  ore,  quite  as 
often  in  gouge.  This  trouble  in  the  vertical  shafts  is  usually  only 
encountered  where  the  shaft  penetrates  the  vein,  as  it  is  adjacent 
to  the  fissures  (whether  filled  with  ore  or  only  with  barren  foliated 
slate  or  gouge)  that  the  rock  swells. 

The  old  Wildman  shaft  at  Sutter  Creek  and  the  Keystone 
main  shaft,  at  Amador  city,  afford  excellent  examples  of  the 
difficulties  and  expense  attending  the  maintenance  of  shafts 
under  the  conditions  met  here.  Both  of  these  famous  old  shafts 
were  originally  timbered  with  heavy  timbers,  but  all  of  the  origi- 
nal timbers  have  been  removed  and  replaced  by  others  many 
times.  The  size  of  the  timbers  was  also  increased  from  time  to 
time,  until  these  shafts  to-day  are  practically  cribbed  for  hundreds 
of  feet  with  great  logs  24  to  30  in.  in  diameter,  and  even  these 
fail  to  hold  the  ground,  but  must  be  removed  from  time  to  time, 
the  ground  relieved  by  cutting  it  away,  and  the  timbers  replaced. 
The  heavy  expense  of  thus  constantly  retimbering  these  old 
shafts  is  enormous.  It  was  estimated  that  the  necessity  of 
operating  through  the  old  Wildman  incline  cost  the  company 
annually  between  $15,000  and  $20,000  more  than  would  have 
been  necessary  had  the  mine  been  equipped  with  a  suitable 
vertical  shaft,  and  it  was  this  fact  that  caused  the  Wildman 
Company  to  commence  sinking  a  large  three-compartment  verti- 
cal shaft. 

We  have  pointed  out  the  danger  and  expense  attached  to 
driving  and  sinking  through  swelling  ground.  It  is  true  that 
usually  both  the  danger  and  expense  come  some  time  after  the 
cutting  has  been  made  —  from  a  few  hours  to  several  weeks,  but 
when  the- pressure  begins  to  assert  itself,  it  is  irresistible,  and 
proper  means  to  deal  with  ground  of  this  kind  must  be  provided, 
or  serious  consequences  will  inevitably  result. 

It  was  learned  long  since,  in  drifts  that  had  been  driven 
through  swelling  ground,  that  timbers  closely  placed,  with  close 
lagging,  could  not  be  depended  upon  to  hold  ground  of  this 
character;  that  the  more  substantially  the  drift  was  timbered, 
and  the  closer  it  was  lagged,  the  more  certain  was  it  that  the 
pressure  upon  the  sets  would  first  cause  the  lagging  to  bend,  and 
later,  if  they  were  not  taken  out,  one  at  a  time,  and  the  ground 
cut  away  with  a  pick,  the  heavy  timbers  would  be  displaced, 


108 


TIMBERING   AND   MINING 


BEARERS  IN  SHAFTS 


109 


bent,  split  or  broken.  This  is  illustrated  in  Fig.  51.  It  took 
years  to  learn  that  this  trouble  and  expense  could  be  almost 
entirely  obviated  if  the  lagging  were  put  in  with  a  space  of  4  to 
6  in.  between;  that  through  these  open  spaces  the  encroaching 
ground  would  slowly  force  itself,  and  that  it  might  readily  be  cut 
away  without  removing  any  of  the  lagging,  and  the  pressure 
upon  the  sets  relieved,  when  necessary,  at  minimum  expense. 
The  principles  employed  in  timbering  drifts  in  this  manner  have 
been  adapted  to  shafts.  It  has  been  learned  that  a  shaft  may  be 
sunk  through  swelling  ground,  and  that  it  may  be  kept  in  almost 
perfect  alinement,  if  only  the  necessary  precautions  be  taken 
when  the  shaft  is  being  sunk.  This  is  accomplished  by  cutting 

] n n n 


. 


U 


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FIG.  52.  —  Longitudinal  Section 


the  opening  large  enough  to  permit  the  building  of  a  "  crib  " 
around  the  shaft  sets,  with  suitable  arrangements  for  relieving 
the  ground  as  the  pressure  asserts  itself. 

The  accompanying  sketches,  Figs.  52  and  53,  illustrate  a 
portion  of  a  shaft  that  is  protected  by  a  crib  built  outside  the  main 
sets,  Fig.  52  showing  a  vertical  section  of  one  side.  The  timbers 
of  the  regular  shaft  set  are  seen  reinforced,  as  it  were,  by  a  second 
end  plate  which  is  separated  from  the  end  plate  of  the  set  by  a 
sprag  (S)  about  24  in.  long.  The  outer  plate  must  be  blocked 
and  wedged  where  necessary,  in  the  same  manner  as  is  usual 
with  shaft  sets.  The  blocking  and  wedges  are  omitted  from  the 
sketches  purposely,  as  these  would  be  placed  where  required. 
Fig.  53  shows  a  plan  of  a  portion  of  the  shaft.  The  lagging  is 
placed  outside  the  outer  plates.  It  should  be  at  least  4  in.  thick 


110 


TIMBERING   AND   MINING 


and  6  to  8  in.  wide.  They  should  not  be  placed  nearer  than 
6  to  8  in.  from  each  other.  Upon  the  sprags  —  one  being  placed 
directly  opposite  each  end  plate,  opposite  each  end  of  the  wall 
plates  and  also  opposite  the  dividers  —  a  platform  of  2-in.  plank 
is  laid,  one  plank  nearest  the  shaft  being  set  upon  edge  to  prevent 
rock  or  earth  from  falling  down  the  shaft  at  any  time.  When- 
ever necessary  men  go  upon  these  platforms  and  cut  away  the 
ground  that  is  pressing  against  the  lagging  and  forcing  its  way 
between  them.  The  lagging  may  be  removed  and  replaced  after 
cutting  out  the  ground.  This  method  of  timbering  makes  the 
work  of  relief  comparatively  easy  and  safe.  As  the  ground  is 
removed  it  falls  upon  the  platform,  from  which  it  can  readily 
be  shoveled  into  a  skip  in  the  shaft.  It  will  be  conducive  to 
safety  to  allow  the  platforms  to  remain  in  place  —  at  least  on  every 


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V'x  8  'Lagging  with  6  Spaces 

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FIG.  53.  —  Transverse  Section 

other  set  —  for  the  purpose  of  catching  any  rocks  or  material 
coming  through  the  spaces  between  the  lagging,  preventing  it 
from  falling  down  the  shaft.  Of  course,  close  lagging  may  be 
spiked  to  the  main  shaft  sets,  if  considered  necessary,  but  if  the 
shaft  be  well  timbered,  in  the  manner  suggested,  in  some  instances, 
at  least,  inside  lagging  will  be  unnecessary. 

Absolute  safety  to  men  in  the  shaft  is  the  first  essential,  the 
consideration  of  economy  being  next,  convenience  in  caring  for 
the  shaft  being  the  last  consideration;  but  to  be  economical  the 
arrangement  must  be  convenient.  In  a  shaft  timbered  as  here 
suggested,  it  will  be  advisable  to  use  permanent  hanging-bolts, 
as  the  ground  in  course  of  time  is  likely  to  exert  unequal  pressure 
and  induce  movement  of  the  shaft  sets,  and  this  tendency  can 
be  much  more  readily  controlled  if  the  timbers  are  solidly  sus- 


BEARERS  IN  SHAFTS  111 

pended  from  bolts.  It  is  probable  that  in  a  deep  shaft  a  crew  of 
two  or  more  men  may  be  required  all  the  time  to  keep  the  shaft 
properly  lined  up.  There  are  mines  on  the  Mother  Lode  of  Cali- 
fornia where  from  four  to  six  men  were  employed  constantly  on 
shaft  relief  and  repairs,  working  under  the  old  system  of  heavy 
timbering  to  resist  pressure.  Whenever  "cribs"  have  been 
introduced,  they  have  effected  a  change  for  the  better  that  was 
at  once  noticeable. 

In  inclined  shafts,  quite  frequently,  the  pressure  is  from  one 
side  only  —  one  side  being  hard  rock.  The  old  Eureka  mine  at 
Sutter  Creek,  for  instance,  has  a  hard,  firm  hanging-wall  of  meta- 
diabase,  and  a  foot  wall  of  soft,  black  slate  that  swells  upon 
exposure.  That  mine  has  been  idle  for  about  30  years,  and  it 
would  be  no  surprise,  should  it  ever  be  reopened,  to  find  that 
practically  all  the  workings  in  the  main  fissure  have  been  com- 
pletely closed  by  the  swelling  slate.  Where  the  swelling  ground 
is  on  but  one  side,  then  the  crib  will  only  be  required  on  the  dis- 
turbed side.  It  has  been  suggested  that  in  such  a  fissure  it  would 
be.  a  good  idea  to  sink  a  shaft  with  the  longer  axis  of  the  shaft 
normal  to  the  fissure,  that  is,  the  end  to  be  in  line  with  the 
direction  of  pressure.  In  a  vertical  shaft  this  scheme  might  be 
introduced  to  advantage,  but  in  an  incline  it  necessarily  contem- 
plates one  compartment  overlying  another,  with  the  pump  and 
manway  compartment  on  the  bottom,  and  the  hoisting  com- 
partments one  above  another,  overlying  the  pump  compartment. 
The  theory  advanced  is,  that  as  a  much  smaller  area  would  be 
directly  exposed  to  the  region  of  pressure,  it  would  be  propor- 
tionally easier  to  hold  the  ground  in  a  shaft  of  relatively  smaller 
sectional  area.  Just  how  this  would  work  out  is  a  question,  but 
it  seems  that  the  pressure,  which  in  all  probability  would  be 
exerted  also  from  the  direction  of  the  strike  of  the  disturbing 
formation,  would  be  likely  to  prove  a  source  of  much  trouble. 

Fenders  for  the  Protection  of  Shaft  Timbers  when  Blasting 

Shaft  sinking  always  requires  that  some  precautions  be  taken 
to  protect  the  timbers  at  the  time  of  blasting,  where  timbers  are 
carried  within  20  ft.  of  the  bottom  or  closer.  This  may  be  done 
in  various  ways,  the  most  common  being  the  hanging  of  green 
pine  timbers  on  chains  beneath  the  plates  of  the  lowest  set;  or 
the  fender  timbers  may  be  suspended  by  means  of  bolts  passed 


112  TIMBERING  AND   MINING 

through  holes  bored  through  the  fenders  and  run  upward  through 
the  unused  hanging-bolt  holes  of  the  lowest  plates  of  the  sets 
above.  The  bolts  should  be  L-shaped,  having  a  thread  cut  at  the 
long  end  only,  so  that  a  nut  provided  with  a  handle  may  be 
screwed  upon  it  to  hold  the  timber  in  place.  The  lower  end 
turned  outward  at  a  right  angle  will  support  the  timber. 

A  third,  and  very  satisfactory  way  is  to  place  steel  plates 
beneath  the  last  set  and  also  on  the  inner  face  of  the  timbers. 
These  steel  plates  should  be  in  sections  and  bent  at  a  right  angle, 
so  that  they  will  protect  both  bottom  and  sides  from  flying  rocks. 
Each  of  the  methods  above  mentioned  affords  some  protection 
to  timbers  of  the  lower  set,  which  is  more  or  less  satisfactory, 
according  to  the  care  used  in  placing  the  fenders,  but  neither 
of  these  schemes  affords  the  slightest  protection  to  sets  above 
the  lowest,  whereas  it  is  of  almost  equal  importance  to  give  some 
protection  to  the  timbers  of  sets  above  for  a  distance  of  25  or 
30  ft.  We  have  known  of  a  wall  plate  in  a  set  25  ft.  above  the 
bottom  of  the  shaft,  and  in  the  third  set  from  the  bottom,  being 
broken  squarely  off  by  a  flying  rock.  The  ground  was  very  hard 
and  No.  1  dynamite  was  used.  Under  these  conditions  rocks 
fly  with  terrific,  force,  and  timbers  must  be  either  very  large  — 
unnecessarily  so  for  the  ground  —  or  be  well  protected  to  with- 
stand the  bombardment  of  rocks  when  blasting. 

The  Cable  Mat 

In  view  of  these  conditions,  it  is  desirable  that  some  sort  of 
protection  be  provided  for  all  the  timbers  near  the  bottom  of 
the  shaft.  This  has  been  successfully  accomplished  by  sus- 
pending a  mat  made  by  weaving  together  sections  of  old  hoisting 
rope.  This  can  easily  be  done  with  rope  up  to  1-in.  diameter. 
A  mat  made  in  this  manner  can  be  drawn  up  by  chains  or  pieces 
of  cable  and  made  fast,  affording  the  best  possible  protection 
to  the  timbers.  In  the  case  of  a  large  shaft,  say  one  of  three 
compartments,  and  measuring  16  ft.  in  length  and  7  ft.  in  width, 
outside  measurements,  the  mat  might  be  made  in  two  sections. 
In  a  single  section,  a  mat  of  this  size,  16  X  7  ft.,  would  require 
about  250  ft.  of  cable;  if  made  of  1-in.  rope  this  would  weigh 
about  400  Ib.  A  similar  mat  made  of  J-in.  rope  would  weigh 
300  Ib.,  and  one  of  f-in.  rope  would  weigh  but  220  Ib.  If  in  two 
sections,  mats  of  rope  of  these  several  diameters  would  weigh 


BEARERS   IN   SHAFTS  113 

approximately  but  one-half  of  the  weights  above  given.  Mats 
in  sections  are  advised  for  convenience  in  handling,  not  only  on 
account  of  the  weight,  but  for  the  reason  that  large  mats  cannot 
readily  be  taken  up  and  down  the  shaft.  They  should  be  divided 
the  long  way  of  the  shaft  —  each  section  made  about  3J  ft.  wide 
by  17  ft.  long.  These,  hung  side  by  side,  will  protect  the  timbers 
in  a  shaft  7  X  16  ft.  outside  of  the  timbers. 

The  mats  should  be  suspended  in  such  a  manner  that  they 
are  not  likely  to  be  unhooked  while  shots  are  discharging,  allowing 
the  mat  to  fall  and  leave  the  timbers  exposed  to  the  destructive 
effect  of  the  blasts.  To  suspend  the  mats,  either  chains  or  pieces 
of  wire  cable  of  f-in.  diameter  are  heavy  enough.  These  should 
be  attached  to  the  mat  by  rings  at  the  corners  and  at  or  near  the 
middle  of  the  sides,  these  latter  preventing  the  mats  from  sagging 
too  much  at  the  center.  The  upper  ends  of  rope  or  chain  should 
be  provided  with  hooks  which  may  be  caught  in  the  hanging- 
bolts  of  the  second  set  from  the  bottom.  The  mats  should  not 
be  drawn  too  close  to  the  timbers,  as  greater  protection  is  afforded 
if  they  hang  a  foot  or  more  below  them.  The  mesh  of  the  mats 
should  not  exceed  9  to  10  in.,  and  if  somewhat  closer,  so  much 
the  better.  Where  these  ingenious  fenders  have  been  used  they 
have  been  found  to  afford  all  the  protection  to  timber  required, 
and  their  use  is  strongly  recommended. 

Extension  Tracks  for  Sinking 

The  employment  of  fenders  for  the  protection  of  shaft  timbers 
has  been  fully  described,  and  their  usefulness  explained  in  detail. 
There  are  other  things  in  shaft  sinking,  which,  small  in  themselves, 
help  to  make  up  the  whole.  It  is  by  a  thorough  understanding 
of  the  details  of  mining  work  that  we  are  enabled  to  accomplish 
the  most  work  in  a  given  time  and  thus  reduce  the  cost  of  the 
operation,  whatever  it  may  be.  In  sinking  vertical  shafts, 
the  removal  of  broken  rock  is  best  accomplished  by  means  of  a 
bucket  guided  by  a  cross-head,  the  method  of  making  and  the 
use  of  which  have  been  previously  explained  and  illustrated.  In 
inclines,  sinking  is  usually  carried  on  by  means  of  a  small  skip, 
though  often  a  bucket  is  used  which  slides  between  two  skids. 
When  the  last  set  of  timbers  is  reached  there  must  be  some  means 
of  continuing  the  skip  or  bucket  to  the  bottom  of  the  shaft,  which 
is  done  either  by  movable  skids  or  by  movable  rails.  This  prac- 


114  TIMBERING   AND   MINING 

tice  has  led  to  the  introduction  of  extension  skids  for  buckets. 
These  are  generally  made  of  wood  and  are  often  so  heavy  that 
the  united  efforts  of  several  men  are  required  to  handle  them, 
the  greatest  trouble  arising  when  they  have  to  be  hauled  up  to  a 
place  of  safety  at  the  time  of  blasting.  Not  only  are  these  exten- 
sion skids  made  of  heavy  timber  (generally  4X6  in.),  but  they 
are  also  often-  seen  shod  with  heavy  iron  straps,  and  the  two 
timbers  are  bound  together  by  means  of  several  heavy  bolts. 
As  a  matter  of  course,  the  skids  should  be  strong  enough  to  carry 
the  loaded  bucket,  but  generally  this  part  of  a  shaft-sinking 
outfit  is  made  unnecessarily  heavy. 

On  the  Mother  Lode  of  California,  shafts  sunk  in  the  fissure 
are  usually  provided  with  wooden  tracks  faced  with  strap-iron. 
The  object  of  this  is  to  provide  a  run-way  for  skips  which  will 
be  more  enduring  than  the  bare  wooden  rails.  It  is  unsafe  to 
use  T-rails  in  these  shafts,  owing  to  the  fact  that  the  ground  is 
constantly  shifting,  and  this  has  been  found  to  render  tracks  of 
T-rail  very  dangerous,  as  the  projecting  end  of  a  rail  may  at  any 
point  in  the  shaft  derail  a  passing  skip. 

In  inclined  shafts,  sunk  in  solid  ground,  we  believe  that  skips 
are  preferable  to  buckets  for  sinking,  and  T-rails  are  always  to 
be  preferred  to  strap-iron  tracks,  except  in  such  ground  as  that 
referred  to  as  occurring  on  the  Mother  Lode. 

Inverted  Rails 

In  sinking  inclined  shafts  in  firm  ground  we  have  found  that 
a  very  convenient  extension  track  may  be  made  by  inverting 
T-rails  and  clamping  them  to  the  rails  of  the  track  above  (see 
Fig.  54).  At  the  upper  end  these  inverted  rails  should  have  the 
base  of  the  rail  forged  flat  and  fitted  by  the  blacksmith,  so  that 
it  offers  no  considerable  obstruction  to  the  passage  of  the  skip 
wheels.  These  rails  should  be  at  least  20  ft.  in  length,  and  they 
should  be  kept  from  spreading  by  means  of  clamp  rods  similar 
to  those  used  on  railway  tracks  at  switches,  which  may  be  easily 
adjusted  whenever  needed.  Any  unevenness  in  the  bottom  of 
the  shaft  does  not  affect  the  usefulness  of  these  extension-track 
rails,  as  they  are  independent  of  each  other,  and  one  may  move 
downward  several  feet  further  than  the  other;  so  that,  no  matter 
how  uneven  the  bottom  of  the  shaft  is,  the  track  may  be  kept 
perfectly  straight  and  at  the  same  angle  as  the  main  track.  It 


BEARERS   IN   SHAFTS 


115 


is  advisable  to  have  several  different  lengths  of  track  when  sink- 
ing —  a  5-ft.  length,  a  10-ft.  length  and  a  15-ft.  length.  These 
are  used  in  turn,  a  longer  replacing  a  shorter  length,  as  sinking 
proceeds;  a  20-ft.  length  being  placed  permanently  when  suffi- 
cient headway  has  been  made. 

Sinking-Ladders 

Another  thing  that  requires  careful  and  constant  attention 
is  sinking-ladders,  and  this  applies  to  both  vertical  and  inclined 
shafts.  Sinking-ladders  should  be  made  of  strong,  light  wood, 
and  iron  steps,  made  of  pipe,  are  advisable,  rather  than  those 
of  wood,  which  break  easily  and  are  not  at  all  adapted  to  the 


FIG.  54 

construction  of  sinking-ladders,  always  subjected  to  more  rough 
usage  than  the  ordinary  ladders  of  the  mine.  What  the  men 
require  is  a  strong  light  ladder  —  one  that  is  durable  and  easily 
handled.  It  is  not  necessary  to  make  these  ladders  more  than 
12  in.  wide  between  the  sides,  though  14  or  16  in.  is  usual  for  the 
permanent  ladders. 

Inclines  in  Hard  Rock 

Thus  far  we  have  said  nothing  of  those  inclined  shafts  sunk 
in  hard  rock  in  which  only  foot-wall  timbers  are  employed,  their 
chief  and  in  fact  their  only  function  being  to  afford  the  necessary 
support  for  carrying  the  tracks,  pipes,  ladders  and  any  other 
equipment  placed  in  the  shaft.  Shafts  of  this  description  are 
not  numerous;  still  there  are  such.  It  is  merely  the  good  fortune 
of  the  mine  owners  that  they  need  no  more  timbers  in  the  shaft 


116  TIMBERING  AND   MINING 

than  those  used  as  foot-wall  plates.  It  is  usual  to  set  up  a  line 
of  props  or  stulls  between  the  compartments  of  a  shaft  of  this 
description,  the  object  being  to  afford  a  line  of  supports  for  the 
signal-bell  cord,  but  principally  to  lessen  the  always  present 
danger  to  men  passing  through  the  shaft,  which  would  be  greatly 
increased  by  the  absence  of  the  line  of  props. 

Shaft  Repairing 

Shaft  repairing  is  often  more  difficult  than  shaft  sinking, 
but  experienced  men  can  generally  overcome  any  difficulty  likely 
to  be  encountered.  It  requires  generally  the  employment  of 
temporary  supports  to  hold  the  ground  while  the  old  timbers 
are  being  removed  to  make  room  for  the  new  ones.  Of  course, 
it  is  important  what  the  nature  of  the  repairs  is.  If  it  is  merely 
the  removal  of  a  single  broken  or  weak  timber,  the  job  can  usually 
be  promptly  accomplished,  and  if  the  time  be  well  chosen  often 
without  materially  delaying  the  work  in  the  mine.  At  other 
times  the  entire  shaft  needs  repairing  —  old  timbers  becoming 
too  weak  through  decay  to  longer  be  safe.  Sometimes  it  is  merely 
necessary  to  reinforce  the  timbers  by  placing  intermediate  sets 
between  those  already  in  place.  The  repairing  of  a  caved  shaft 
is  a  much  more  dangerous  undertaking  and  often  calls  for  all  the 
skill,  ingenuity  and  bravery  of  which  the  timber  crew  is  possessed. 
An  instance  of  this  character  was  furnished  a  few  months  ago 
at  the  Alpha  shaft  of  the  Giroux  Consolidated  mines  at  Ely, 
Nevada,  where  several  hundred  feet  of  the  shaft  was  lost  by 
caving,  but  which  was  recovered  by  the  prompt  and  heroic  work 
of  chosen  men  who  labored  unceasingly  to  rescue  those  im- 
prisoned below.  The  history  of  mining  has  furnished  many  such 
instances  of  the  skill  and  heroism  of  miners.  They  are  never 
found  wanting  when  human  life  is  at  stake. 


CHAPTER  XI 


POSITION   AND   DIRECTION   OF   DRILL  HOLES   IN 
SHAFT   SINKING 

THE  disposition  of  drill  holes  and  their  direction  in  sinking 
shafts  is  of  importance.  In  handwork  this  is  done  with  particular 
reference  to  each  part  of  the  shaft,  and  the  holes  will  vary  more 


FIG.  55.  —  Showing  Direction  of  Drill  Holes 

or  less  with  each  round,  both  as  to  the  number  of  holes  drilled 
and  their  direction   and  depth.     But  in   machine  drilling  it  is 


FIG.  56.  —  Disposition  of  Drill  Holes 

customary  to  drill  the  full  round  before  blasting,  whether  the 
entire  round  be  fired  at  once  or  not.  When  machines  are  em- 
ployed, the  holes  should  be  arranged  systematically,  in  order  to 
secure  the  best  results  with  the  least  expenditure  of  time  and 
money.  Figs.  55  and  56  illustrate  the  usual  manner  of  placing 
holes.  Two  separate  shafts  are  shown  —  one  18  X  8  ft.,  the  other 
22  X  13  ft.,  outside  of  timbers.  Obviously,  more  holes  are  gen- 
erally required  to  break  the  rock  in  a  shaft  of  large  section 

117 


118  TIMBERING   AND   MINING 

than  in  a  small  one.  The  holes  nearest  the  center  (the  "cut") 
are  fired  first,  then  the  others,  either  in  series  or  simultaneously. 

Many  engineers  believe  that  shaft  sinking  can  be  accomplished 
more  rapidly  and  at  less  expense  by  drilling  the  "cut"  holes 
near  one  end  of  the  shaft,  and  firing  the  blasts  in  series  from  the 
cut  across  the  cutting  toward  the  opposite  end.  This  usually 
results  in  throwing  the  muck  pretty  well  to  one  end  of  the  shaft, 
so  that  by  mucking  at  the  end  where  there  is  the  least  debris, 
space  is  soon  made  to  set  up  machines  and  continue  drilling  while 
shovelers  clean  up  the  opposite  end.  This  was  done  at  the 
Hoatson  shaft  of  the  Superior  and  Pittsburg  Company,  at  Bisbee, 
Arizona,  and  a  record  for  shaft  sinking  established  for  that  dis- 
trict in  the  Hoatson  shaft. 

In  some  shafts,  firing  is  done  by  electricity.  Ordinarily  this 
is  a  satisfactory  and  safe  method  of  firing  blasts,  but  there  are 
some  objections  to  the  practice  when  timber  has  to  be  carried 
close  to  the  bottom  of  the  shaft,  as  the  terrific  concussion  fre- 
quently does  much  damage  to  the  timbers,  causing  delays  and  ex- 
pense which  might  have  been  obviated  by  cutting  the  fuses  to 
suitable  lengths  —  the  short  ones  in  the  cut  holes  and  longer  ones 
nearer  the  ends.  Where  the  holes  are  fired  in  series,  electricity 
may  be  safely  used,  and  in  shafts  where  the  timbers  are  not  too 
close  to  the  bottom,  there  is  an  advantage  in  simultaneously 
discharging  the  entire  round  by  the  electric  method.  Several 
attempts  have  been  made  to  manufacture  electric-firing  apparatus 
which  will  fire  blasts  in  series,  by  a  differentiation  of  the  in- 
tensity of  the  current  or  by  wires  of  differing  resistances,  but 
thus  far  these  attempts  have  not  been  an  unqualified  success. 
The  idea  may  yet  be  perfected. 


CHAPTER  XII 

CUTTING   AND   TIMBERING  STATIONS   AT   SHAFTS 

NOT  the  least  important  matter  in  the  sinking  and  equipment 
of  shafts  is  the  cutting  and  arrangement  of  stations.  In  recent 
years  it  has  come  to  be  recognized  that  much  in  the  economy  of 
mine  operation  depends  upon  the  arrangement  of  the  station. 
It  is  not  so  very  long  since  it  was  a  common  thing  to  see  stations 
at  the  shafts  of  important  mines  merely  an  enlargement  of  the 
drift,  affording  a  safe  passage  for  the  workmen  to  pass  the  shaft 
in  going  from  one  side  to  the  other.  Often  the  only  arrangement 
for  handling  ore  consisted  of  a  small,  sloping,  open  chute,  with 
an  extension  of  a  few  inches  into  the  shaft,  this  projection  or 
apron  being  sometimes  fixed,  arid  in  other  cases  provided  with 
hinges  so  that  it  may  be  turned  back  or  dropped  down,  out  of 
the  way  of  the  skip  or  bucket.  When  it  was  desired  to  load 
the  skip  or  bucket  with  ore,  it  was  stopped  at  the  level  and  a  car 
of  ore  was  dumped  upon  the  chute,  from  which  it  ran  or  was 
scraped  into  the  waiting  skip  or  bucket.  This  was  a  crude  and 
unsatisfactory  method  of  handling  ore,  and  it  is  evident  that  it 
was  impossible  to  handle  a  large  tonnage  in  this  manner.  As  a 
matter  of  fact,  comparatively  few  mines  were  equipped  in  this 
fashion;  still  they  were  numerous  enough,  and  it  was  one  of  the 
recognized  methods  of  ore  handling  at  shafts. 

Cages,  upon  which  cars  are  run,  have  been  in  use  for  many 
years,  having  first  been  introduced  in  Europe,  where  the  cages 
are  generally  ponderous  affairs.  In  America  the  cage  is  made 
of  steel,  is  light  and  durable,  and  affords  a  very  satisfactory 
means  of  handling  ore.  Cages  are  made  with  one,  two,  three, 
and  even  four  decks,  so  that  several  cars  may  be  run  in  turn 
upon  the  platforms  of  the  cage,  and  hoisted  at  one  time.  When 
cages  were  first  introduced,  about  1860,  they  were  at  once  recog- 
nized as  so  superior  to  the  old  shoveling  and  flat-chute  arrange- 
ments that  there  was  "  no  comparison  "  between  cages  and  former 

119 


120  TIMBERING  AND   MINING 

methods.  In  referring  to  the  introduction  of  cages  in  mines  on 
the  Comstock  Lode,  Dr.  R.  W.  Raymond  said,  in  his  report  to 
Congress,  1870:  "The  mineral,  having  been  taken  to  the  shaft, 
is  either  dumped  in  a  pile  and  then  shoveled  into  the  bucket  or 
skip,  or  is  dumped  through  a  chute  directly  into  the  skip,  and  the 
empty  car  is  returned  to  the  face.  But  this  necessitates  a  re- 
handling  of  the  mineral,  which,  when  it  reaches  the  surface, 
must  be  dumped  again  into  a  car  or  wagon,  by  which  it  can  be 
delivered  at  the  proper  point  away  from  the  shaft.  These,  and 
other  considerations,  have  led  to  hoisting  the  car  and  load  to- 
gether to  the  mouth  of  the  shaft.  This  effects  a  great  saving  of 
time  and  labor,  and  wear  and  tear  of  apparatus.  It  is  the  method 
adopted  in  the  mines  upon  the  Comstock  Lode,  and  in  all  well- 
appointed  vertical  shafts  of  any  considerable  depth  elsewhere." 

Ore  Pockets  Beneath  the  Levels 

This  was  before  the  day  of  cutting  ore  pockets  beneath  the 
stations,  and  before  the  day  of  automatically  loading  and  dump- 
ing skips.  It  is  true  that  skips  had,  even  prior  to  that  time 
(1870),  been  arranged  to  dump  automatically  upon  reaching  the 
surface,  but  the  skips  were  comparatively  small,  and  the  running 
speed  of  the  hoisting  engines  was  not  great. 

.  To-day  the  ore  pocket  beneath  the  stations,  skips  of  large 
capacity,  fast-winding  engines,  and  automatic  devices,  have 
come  to  be  recognized  as  necessary  to  the  economical  hoisting 
and  handling  of  ore.  So  important  has  this  become,  and  so  great 
the  decrease  of  cost  from  that  of  hoisting  by  cages,  that  many  of 
the  largest  and  deepest  mines  of  the  United  States  have  within 
a  recent  period  made  expensive  changes  in  their  shafts,  and  have 
substituted  skips  for  cages.  Among  the  mines  having  made  or 
making  this  change  are  several  at  Butte,  Montana,  the  Calumet 
and  Hecla  copper  mine  at  Houghton,  Michigan,  with  its  mile- 
deep  shafts;  the  Copper  Queen  mine,  at  Bisbee,  Arizona,  and  the 
Homestake,  at  Lead,  South  Dakota.  It  is  not  a  matter  of  pref- 
erence, merely,  but,  it  has  been  clearly  and  repeatedly  demon- 
strated that  hoisting  a  given  tonnage  with  skips  can  be  done 
more  rapidly  and  at  less  expense  than  by  any  other  means  at 
present  in  use. 

Stations  should  be  cut  at  the  time  of  sinking.  When  the  shaft 
reaches  the  point  where  it  has  been  decided  to  establish  a  level, 


CUTTING   AND   TIMBERING   STATIONS  AT  SHAFTS        121 

the  ground  should  be  broken  out  a  few  feet  on  that  side  where  it 
has  been  planned  to  cut  the  station.  Working  room  only  need 
be  provided,  which  is  at  the  time  sufficient.  The  work  of  sinking 
should  be  continued  until  the  shaft  has  been  completed  to  a  depth 
of  at  least  30  ft.  below  the  floor  of  the  level  it  is  intended  to  estab- 
lish. In  the  fifth  or  sixth  set  below  the  level,  strong  chutes 
should  be  built.  It  is  well  to  provide  these  with  steel  doors, 
operating  with  rack  and  pinion.  When  all  is  completed,  and  there  is 
sufficient  room  to  accommodate  the  skip  beneath  the  lip  of  the 
chute,  the  miners  may  go  into  the  recess  back  of  the  timbers, 
and  for  protection  line  up  the  shaft  sets  with  heavy  green  logs, 
or  old  T-rails,  and  proceed  to  cut  out  the  sloping  floor  of  the  ore 
pocket.  This  should  have  an  angle  of  at  least  45  degrees,  so  that 
if  the  bottom  of  the  chute  is  25  ft.  below  the  level,  the  inclined 
bottom  of  the  pocket  will  extend  backward  to  the  door  of  the 
level  at  least  25  ft.  from  the  shaft.  The  miner  should  at  first 
do  all  drilling  by  hand  until  sufficient  room  has  been  made  to 
employ  machines,  by  which  latter  means  two-thirds  of  the  work, 
at  least,  may  be  done.  It  will  always  be  necessary  to  protect 
the  shaft  timbers  as  far  as  possible  from  injury  by  blasting,  and 
for  this  reason  holes  must  be  pointed  and  loaded  with  good  judg- 
ment, avoiding  the  use  of  an  excess  of  powder.  The  writer  has 
had  stations  cut  in  shafts  that  had  been  sunk  several  hundred 
feet  below  the  level  of  the  station,  and  little  injury  to  the  shaft 
sets  resulted,  where  precautions  were  taken  to  avoid  it,  so  that 
we  know  work  of  this  kind  can  easily  be  done  by  experienced 
miners. 

The  character  of  the  ground  to  be  removed  may  have  an  im- 
portant influence  on  the  methods  employed  and  on  the  speed  of 
the  work,  for  it  may  be  necessary  to  put  in  many  temporary 
timber  supports  to  hold  ground  until  the  main  timbers  can  be 
placed.  It  will  be  evident  that  all  rock  broken  in  the  station 
from  the  bottom  of  the  ore  pocket  to  the  roof  of  the  station  may 
be  drawn  out  through  the  chute  doors,  thus  dispensing  with 
much  shoveling  and  consequently  reducing  the  cost  of  cutting 
the  station.  Even  of  the  rock  blasted  in  cutting  the  station 
itself,  back  of  the  top  of  the  inclined  bottom  of  the  ore  pocket, 
the  greater  part  will  fall  into  the  pocket  and  may  be  drawn  into 
the  skips  without  shoveling  a  pound  of  rock.  The  method  applies 
to  either  inclined  or  vertical  shafts. 


122  TIMBERING  AND  MINING 

Stations  should  be  roomy — there  is  little  economy  in  cutting 
them  too  small.  The  station  should  be  at  least  as  wide  as  the 
shaft,  and,  on  the  side  adjacent  to  the  hoisting  compartment, 
should  extend  fully  two  feet  beyond  the  shaft.  This  affords  a 
safe  landing  place  for  men,  who  may  step  from  the  skip  upon  the 
platform  at  the  side  of  the  shaft  instead  of  directly  in  front, 
where  there  is  sometimes  danger  of  falling  into  the  ore  pockets 
beneath.  The  space  at  the  side  also  affords  convenient  room  in 
handling  materials  going  into  or  coming  out  of  the  skips,  and  this 
applies  to  inclined  shafts  as  well  as  to  those  that  are  vertical. 

In  height  the  station  should  be  not  less  than  12  ft.  at  the  shaft. 
This  is  absolutely  necessary  in  stations  at  vertical  shafts,  and  even 
a  greater  height  is  often  an  advantage.  In  inclines,  stations 
may  be  somewhat  lower,  but  unless  the  shaft  be  very  flat  —  less 
than  40°  —  it  is  a  mistake  to  cut  the  station  less  than  10  ft.  high 
adjacent  to  the  shaft.  This  permits  the  unloading  of  long  lengths 
of  pipe,  rails  and  long  timbers,  for  which  there  must  be  sufficient 
head  room.  Every  shaft  station  should  be  equipped  with  a  strong 
block  and  tackle,  for  the  convenient  removal  of  heavy  articles 
from  the  skip.  The  block  and  tackle  is  suspended  from  the  roof 
of  the  station,  properly  from  a  stout  hook,  one  opposite  each 
hoisting  compartment.  Where  machinery  is  to  be  handled, 
chain  blocks  should  be  provided.  These  little  conveniences 
greatly  facilitate  and  cheapen  labor,  and  failure  to  place  them  in 
stations  is  mistaken  economy. 

From  10  to  12  ft.  back  from  the  shaft  the  roof  of  the  station 
may  be  somewhat  lower,  though  it  seems  to  be  a  mistake  to  ever 
cut  the  opening  less  than  9  ft.  clear  of  the  track.  A  low  back 
in  a  station  has  many  disadvantages.  It  directly  affects  ventila- 
tion, and  is  often  regrettable,  particularly  where  long  pipes  and 
timbers  are  to  be  handled.  In  width  the  station  should  be,  as 
previously  stated,  as  wide  as  the  shaft,  and  the  width  should  be 
maintained  well  back  of  the  ore  pockets.  At  the  rear  end  it  is 
a  good  idea  to  have  a  stout  work  bench,  provided  with  a  vise  and 
other  tools,  and  a  small  stock  of  pipe  fittings  may  be  carried  in 
boxes  arranged  above  the  work  bench.  This  is  to  facilitate  the 
making  of  small  repairs  to  pipe  lines  or  to  ventilating  apparatus. 
The  repairing  of  machine  drills  should  be  done  in  the  machine 
shop  on  the  surface,  unless  the  mine  be  provided  with  a  fully 
equipped  shop  and  forge  underground  —  a  practice  that  in  recent 


CUTTING  AND   TIMBERING   STATIONS  AT   SHAFTS        123 

years  has  been  quite  generally  adopted  in  many  large  mines.  In 
the  Homestake  mine  at  Lead,  South  Dakota,  there  are  two  large 
and  well-equipped  shops  underground,  one  at  the  500  level  and 
one  at  800.  In  these  shops  all  ordinary  repairs  are  made,  hun- 
dreds of  drills  are  sharpened  daily  by  mechanical  drill  sharpeners, 
and  much  work  done  which  would  otherwise  go  to  the  shops  on 


FIG.  57 

the   surface.     The   saving   in   time    and   otherwise    amounts   to 
thousands  of  dollars  annually. 

In  small  mines  it  is  customary,  whether  it  be  good  practice 
or  not,  to  cut  fuses  and  fit  them  with  caps  at  the  work  bench  in 
the  station,  and  in  numerous  instances  the  criminal  practice  of 
keeping  several  boxes  of  powder  in  the  station  is  permitted. 
This  latter  should  be  prohibited  by  law,  as  many  fatal  accidents 
are  directly  due  to  the  careless  handling  of  powder  at  stations. 


124 


TIMBERING  AND   MINING 


Powder  and  caps  should  always  be  kept  in  separate  places,  and 
while  it  is  true  the  powder  can  easily  be  exploded  without  the 
presence  of  the  caps,  the  danger  is  greatly  increased  by  having 
the  two  in  close  proximity.  It  is  the  best  way  to  have  a  small 
room  in  a  dry  place  in  each  level  where  the  fuse  and  caps  may  be 
prepared  by  a  man  whose  duty  it  is  to  attend  to  this,  and  the 
powder  should  be  kept  in  a  separate  place  and  away  from  the 
main  lines  of  traffic  of  the  mine  —  an  abandoned  drift  or  cross- 
cut, or  a  chamber  cut  out  especially  for  storage  of  powder,  and 
the  amount  of  explosive  placed  in  such  an  underground  magazine 
should  be  but  little  more  than  is  necessary  for  the  day's  work. 


FIG.  58 


The  observance  of  these  simple  suggestions  would  undoubtedly 
prevent  many  accidents  from  premature  explosion,  for  disastrous 
results  have  followed  in  scores  of  mines  where  these  precautions 
have  been  neglected. 

Of  course,  stations  cut  in  hard  rock  require  comparatively 
little  timber,  but  in  some  mines  this  fortunate  condition  does 
not  exist,  and  the  stations  require  more  or  less  elaborate  timber- 
ing. No  rule  need  be  laid  down  for  the  timbering  of  stations, 
as  the  timbermen  will  naturally  employ  such  methods  as  the 
conditions  require.  The  principles  underlying  the  timbering 
of  underground  excavations  will  govern  in  the  sustaining  of 
stations  as  well  as  other  cuttings. 


CUTTING  AND   TIMBERING   STATIONS  AT  SHAFTS        125 

Types  of  Stations  at  Inclined  and  Vertical  Shafts 

Having  said  all  that  it  seems  necessary  to  say  about  stations 
at  both  vertical  and  inclined  shafts,  we  here  illustrate  the  two 
types,  each  as  representative  of  its  class.  In  the  sketch  of  the 
station  at  the  vertical  shaft,  Fig.  57,  it  will  be  noticed  that  there 
is  a  considerable  recess  between  the  front  of  the  ore  pocket  and 
the  shaft  proper.  While  it  reduces  materially  the  storage  capacity 
of  the  pocket,  it  affords  opportunity  for  prompt  repairs  about 
the  timbering  of  the  pocket,  and  also  provides  a  safe  place  for 
the  skip-tender  while  in  the  performance  of  his  duties  in  signal- 
ing and  loading  skips.  These  two  points  are  distinctly  in  favor 
of  constructing  loading-bins  and  chutes  beneath  stations  after 
the  manner  here  suggested. 

The  sketch  of  the  station  at  an  inclined  shaft,  Fig.  58,  is  a 
duplicate  of  those  made  under  the  direction  of  the  writer  in  a 
mine  in  Amador  County,  California,  and  which  were  found  to 
meet  every  requirement.  The  pocket  was  divided  by  a  partition 
through  the  center  so  that  when  desirable  waste  could  be  dumped 
in  one  side  and  ore  in  the  other.  When  no  waste  is  being  sent  to 
the  surfaces,  both  sides  may  be  used  for  ore. 

Draining  by  Means  of  Skips  and  Tanks 

At  the  rear  of  the  station,  and  beneath  the  level,  is  seen  an 
excavation,  cut  as  a  sump  to  catch  the  water  coming  to  the 
station  from  that  level.  A  trench  was  cut  through  the  rock  con- 
necting the  sump  with  the  ore  pocket  and  a  6-in.  pipe  laid  from 
the  sump  to  the  shaft.  The  pipe  was  given  a  very  small  grade, 
and  at  the  end  was  secured  a  piece  of  canvas  hose  about  3  ft.  long. 
A  plank  and  clay  dam  made  the  end  of  the  tank  tight.  A  loop  of 
rope  was  made  fast  to  the  end  of  the  hose  so  that  it  might  be  hung 
up  when  not  in  use,  the  end  then  being  higher  than  the  valve 
at  the  further  end  of  the  pipe,  though  if  desired  it  may  be  higher 
than  the  level  of  the  water  in  the  tank.  The  flow  of  water  was 
controlled  by  a  simple  clack-valve  placed  at  the  end  of  the  pipe 
and  submerged  in  the  sump.  This  was  operated  by  a  rope  which 
passed  upward  to  the  roof  of  the  level  and  thence  along  the  station 
and  down  the  shaft,  where  the  skip-tender  could  manipulate  it 
conveniently.  When  the  skip  arrived  he  simply  unhooked  the 
hose,  dropped  the  end  into  the  skip,  and  pulled  the  valve  rope. 


126 


TIMBERING   AND   MINING 


The  water  rushed  through  the  pipe  into  the  skip.  When  it  was 
about  full  the  rope  was  released,  the  valve  closed,  the  hose  after 
draining  a  little  is  hung  up,  and  the  skip  rung  away. 

Mr.  Hans  C.  Behr,  in  his  excellent  work  on  "Mine  Drainage 
Pumps,"  Bulletin  No.  9,  of  the  State  Mining  Bureau  of  California, 
illustrates  a  well-arranged  sump  and  its  attachments  for  draining 
a  mine  in  this  manner.  The  sketch  (Fig.  59)  is  from  his  book. 


FIG.  59 

It  should  be  stated  that  when  the  pipe  from  the  sump  to  the  shaft 
passes  through  the  ore  pocket,  it  must  be  protected  from  rocks 
dumped  into  the  pocket  from  the  cars  on  the  level  above.  This 
may  be  done  by  running  the  pipe  either  through  the  center  of 
the  pocket  next  to  the  partition,  or  at  one  side  adjacent  to  the 
wall  of  the  pocket.  In  either  case  it  should  be  protected  in  such 
a  way  that  it  will  be  shielded  from  impact  of  the  rocks. 

While  speaking  of  mine  drainage  it  seems  advisable  to  again 
call  attention  to  the  advantages  of  bailing.  We  have  referred 
to  this  heretofore,  but  believe  its  importance  justifies  further 


CUTTING  AND  TIMBERING  STATIONS  AT  SHAFTS        127 

mention  of  it.  Mr.  Behr,  in  the  work  above  referred  to,  has  de- 
voted considerable  space  to  the  subject,  and  several  of  the  sketches 
accompanying  his  remarks  are  reproduced.  He  says: "  The  simplest 
method  of  raising  water  from  deep  mines  is  by  means  of  bailing 
tanks  which  may  take  the  water  either  from  station  reservoirs  or 
from  the  sump.  In  the  latter  case  they  are  either  made  self- 


U 


FIG.  60 


FIG.  61 


filling,  or  are  filled  by  means  of  pumps  or  other  contrivances. 
Rapid  filling  of  bailing  tanks  is  very  important.  Figs.  60  and  61 
illustrate  types  of  tanks  fitted  with  a  valve  in  the  bottom,  which 
opens  of  itself  when  the  tank  sinks  in  the  sump  water.  Such  a 
method  requires  a  considerable  depth  of  sump  in  order  to  fill 
them,  and  tanks  are  not,  therefore,  adapted  for  sinking  unless 
artificial  means  be  used  to  fill  them, 


128 


TIMBERING   AND   MINING 


"The  discharge  from  bailing  tanks  at  the  surface  or  at  a 
drain  tunnel  must  be  effected  in  such  manner  that  none  of  the 
water  will  fall  down  the  shaft  again.  The  bucket  in  Fig.  60  has 
a  downwardly  projecting  stem  on  the  valve,  which  strikes  the 


FIG.  62 


floor  and  lifts  the  valve  when  the  bucket  is  lowered  into  the  dis- 
charge sluice,  thus  permitting  the  water  to  escape.  Bailing 
tanks  guided  in  vertical  shafts  usually  have  side  valves,  as  in 
Fig.  61,  and  these  sometimes  have  attached  a  hose  which  leads 


CUTTING  AND   TIMBERING   STATIONS  AT  SHAFTS        129 

the  water  into  the  discharge  sluice.  The  most  rapid  manner 
of  discharging  bailing  tanks  is  to  construct  them  like  skips,  so 
that  they  will  dump  automatically  as  they  are  hoisted  above 


FIG.  63 


the  collar  of  the  shaft.  Fig.  62  shows  a  self-dumping  skip  for  a 
vertical  shaft  which  may  be  used  for  either  ore  or  water,  and  Fig. 
63  illustrates  a  simple  skip  used  for  inclines.  The  method  of 


130 


TIMBERING   AND   MINING 


_4_ 


64 


CUTTING   AND   TIMBERING   STATIONS  AT   SHAFTS        131 

dumping  these  skips  is  also  shown."  (Fig.  62  illustrates  the 
Comstock  skip,  and  Fig.  63  that  in  common  use  on  the  Mother 
Lode  of  California.) 

Bailing  by  skips  connected  tandem  is  practised  in  some  of 
the  large  Pennsylvania  coal  mines.  Both  the  details  of  con- 
struction and  methods  of  dumping  are  shown  in  Figs.  64  and  65. 


132 


TIMBERING   AND   MINING 


FIG.  65 


CHAPTER  XIII 

MINING   LARGE  ORE   BODIES   BY  THE  OPEN-CUT  OR 
" GLORY-HOLE"   SYSTEM 

THE  great  majority  of  mines  are  opened  on  comparatively 
small  veins  of  ore,  and  these  are  developed  and  operated  for  most 
part  through  adits  —  tunnels  run  from  the  surface  on  the  vein  — 
or  across  the  formation  to  the  vein,  and  drifts  then  turned  on  it; 
or  the  vein  is  attacked  through  a  shaft,  either  vertical  or  inclined. 
Comparatively  few  small  veins  are  worked  by  open  pits,  though 
there  are  such  in  numerous  places.  Occasionally,  veins  worked 
in  this  manner  do  not  carry  their  value  to  depth,  and  in  such 
instances  deep  workings  are  unnecessary. 

Large  veins  and  deposits  outcropping  at  the  surface  are 
generally  worked  at  and  near  the  surface  by  open  pits.  The 
particular  method  selected  in  the  mining  and  handling  of  ore  in 
these  large  open  excavations  generally  depends  somewhat  upon 
the  topography  of  the  ground  immediately  adjacent  to  the  mine. 
It  is  the  best  practice,  where  possible,  to  drive  a  tunnel  into  the 
ore  body  and  connect  with  a  shaft  sunk  from  the  surface.  If 
the  tunnel  level  is  the  lowest  in  the  mine  at  the  time  this  work  is 
done  (it  generally  is)  a  chute  should  be  built  at  the  foot  of  the 
shaft  or  raise  to  facilitate  the  loading  of  cars.  This  chute  should 
be  strongly  but  not  elaborately  made.  That  is,  no  unnecessary 
expense  should  be  incurred,  as  in  most  cases  it  is  only  a  temporary 
arrangement,  to  be  torn  out  as  soon  as  the  excavation  of  ore  has 
reached  the  level  of  the  chute  or  has  passed  the  limit  of  conven- 
ience. The  raise  or  shaft  connecting  with  the  tunnel  should  not 
be  vertical.  Many  think  that  a  vertical  cutting  of  this  descrip- 
tion is  the  shortest  and  most  direct  way  to  make  connections, 
and  so  it  is;  but  while  vertical  shafts  possess  some  advantage  over 
inclines  for  the  purpose  of  hoisting  ore,  they  are  not  satisfactory 
as  ore  passes,  for  if  a  vertical  chute  becomes  filled  with  ore,  the 
chances  of  its  jamming  are  excellent,  and  once  in  this  unfortunate 

133 


134  TIMBERING   AND   MINING 

condition  there  are  few  miners,  even  the  boldest,  who  relish  the 
job  of  starting  the  rock  again.  It  has  been  found  by  experience 
that  an  ore  pass  cut  at  50  to  55  degrees  is  the  most  satisfactory, 
and  while  chutes  at  this  angle  also  jam,  they  do  so  much  less  fre- 
quently than  those  that  are  vertical. 

When  the  connection  has  been  made  from  the  tunnel  to  the 
surface,  and  the  chute  has  been  built,  the  mining  of  ore  may  pro- 
ceed. The  first  thing  to  be  done  is  to  enlarge  the  shaft  at  the 
top  by  drilling  holes  and  shooting  them  with  small  charges  of 
powder,  the  object  being  to  break  the  ore,  but  not  to  clog  the  chute 
by  allowing  too  large  pieces  to  fall  into  it.  The  process  of  en- 
larging this  hole  continues,  and  when  it  has  been  carried  down 
several  feet  —  twenty  or  more,  a  grizzly  of  logs  should  be  put 
in  to  prevent  large  pieces  going  down  into  the  mill  hole.  These 
are  retained  on  the  grizzly,  where  they  may  be  broken  up  with 
hammers,  or  "  bulldozed "  to  a  size  which  will  pass  the  grizzly. 
In  many  places  the  practice  is  to  connect  the  tunnel  below  with 
the  floor  of  a  cut  already  excavated,  placing  the  grizzly  at  the 
level  of  the  cut.  For  a  time  it  may  be  that  the  rock  blasted  down 
from  the  sides  of  the  cut  may  fall  or  be  shoveled  directly  upon 
the  grizzly,  the  large  pieces  being  broken  up,  but  in  time  the  work- 
ing face  will  advance,  and  then  either  the  grizzly  must  be  extended 
or  tracks  must  be  laid  to  the  working  face,  where  the  ore  is  shoveled 
into  cars  which  are  trammed  to  the  chute  and  dumped.  In  the 
latter  case  no  grizzly  is  required,  as  the  large  rocks  are  broken 
up  before  being  shoveled  into  the  cars. 

Where  the  ore  face  is  high,  and  a  large  amount  of  ore  is  avail- 
able for  a  single  chute,  it  is  a  good  idea  to  have  the  raise  come  up 
at  an  angle  from  beneath  the  working  face,  instead  of  toward  it. 
When  arranged  as  here  suggested,  the  ore  may  be  sent  down 
through  the  grizzly  with  a  minimum  of  shoveling  by  simply 
extending  the  grizzly  as  the  work  advances,  the  ground  over- 
hanging the  chute  being  cut  out  from  time  to  time  as  required. 
At  many  mines  grizzlies  are  dispensed  with  entirely,  all  the  ore 
broken  in  the  cut  being  shoveled  into  cars  and  sent  to  mill,  either 
by  dumping  into  a  mill  hole  or  tramming  to  a  chute  outside  the 
cut.  Often  the  breaker  floor  of  the  mill  is  on  a  level  with  the  cut, 
so  that  the  ore  is  trammed  directly  to  the  mill,  being  handled 
but  once.  Where  waste  that  may  be  sorted  out  is  mixed  with  the 
ore,  it  is  better  to  shovel  into  cars,  separating  the  waste  by  hand. 


MINING  LARGE  ORE  BODIES 


135 


Where  this  is  necessary  the  tracks  should  be  provided  with  several 
branches,  an  ore  car  to  occupy  one  branch  and  a  "stone-boat" 
the  other.  As  shoveling  proceeds,  the  ore  is  thrown  into  the  car 


and  the  waste  piled  on  the  stone-boat  for  such  disposition  as  may 
be  desired.  Where  there  are  underground  stopes  in  the  mine, 
below  the  open-cut  level,  the  waste  should  be  dumped  into  a 
chute  connecting  with  such  stope,  where  it  may  be  utilized  as 
filling. 


136  TIMBERING  AND  MINING 

Among  large  mines  employing  the  open-cut  and  mill-hole 
system  are  the  Homestake,  of  South  Dakota,  the  Big  Indian, 
near  Helena,  Montana  (see  illustration),  the  Yellow  Aster,  at 
Randsburg,  California,  and  the  Treadwell,  Alaska.  Those  men- 
tioned have  mined  a  very  large  amount  of  ore  by  this  method,  and 
afford  excellent  examples  of  this  practice.  We  consider  the  gen- 
eral method  in  vogue  at  the  Yellow  Aster  superior  to  most  others, 
as  more  attention  has  been  given  to  the  details  of  preparation  and 
the  result  is  eminently  satisfactory. 

Cheap  mining  is  done  at  all  of  the  places  mentioned  by  the 
"glory-hple"  method.  The  term  glory  hole  originated  at  the 
Treadwell  mine,  on  Douglas  Island,  Alaska.  So  many  miners 
employed  in  the  great  open  cuts  were  killed  by  tumbling  down  the 
cliffs,  or  were  knocked  over  by  falling  rocks,  that  the  cuts  were 
called  glory  holes,  as,  presumably,  the  poor  fellows  went  to  glory 
numerously  and  suddenly.  Ordinarily,  the  open-cut  method  of 
mining  is  not  excessively  dangerous.  Often  the  greatest  element 
of  danger  is  the  bulldozing  of  large  rocks,  and  the  danger  from 
this  source  is  increased  by  the  insane  practice  of  placing  rocks 
of  5  to  10  pounds  weight  on  the  charge  of  powder  and  fuses  "to 
keep  them  from  being  jarred  off."  At  times  of  bulldozing,  the 
air  is  filled  with  rock  fragments  for  several  hundred  yards,  and 
men  are  frequently  hurt  who  considered  themselves  at  a  safe 
distance;  in  most  cases  they  would  be  safe  from  blasting,  but  it 
is  the  small  loose  rocks  that  constitute  the  greatest  menace. 

The  sketch,  Fig.  67,  represents  partly  the  present  practice, 
and  in  part  the  prospective  method  of  mining  at  the  Yellow  Aster 
mine,  at  Randsburg,  California.  The  upper  half  of  the  drawing 
is  intended  to  illustrate  the  method  at  present  in  vogue  there, 
and  the  lower  part  the  method  that  in  all  probability  will  be  in- 
troduced later,  when  the  large  open  cut  is  extended  to  greater 
depth,  about  115  ft.  lower  than  the  floor  of  the  cut  where  the 
principal  out-door  operations  are  now  being  carried  on. 

At  present  the  ore  broken  down  in  the  faces  of  the  great  cut 
either  falls  directly  upon  or  near  grizzlies  covering  mill  holes, 
conveniently  disposed  at  various  points  about  the  great  excava- 
tion, or  it  is  shoveled  at  the  base  of  the  ore  face  into  cars  and 
trammed  to  the  nearest  mill  hole,  through  which  it  descends  by 
gravity  to  the  loading  chutes  situated  on  the  level  below.  In 
order  to  continue  the  method  of  mining  by  open  cut,  it  will  soon 


MINING  LARGE  ORE  BODIES 


137 


become  desirable,  if  not  necessary,  to  carry  excavation  below  the 
present  level,  called  the  Trilby.  On  the  Rand  level,  which  is  the 
lowest  adit  level  of  the  mine  at  this  time,  trains  of  cars,  drawn 


Open  Cut 


FIG.  67 


by  a  motor,  enter  the  mine  and  by  a  rudely  circular  route  pass  a 
series  of  loading  chutes  which  connect  by  mill  holes  with  the  open 
cut  on  the  Trilby  level  and  with  certain  underground  stopes  on 
the  Trilby  level,  and  at  others  intermediate  between  that  and  the 


138  TIMBERING  AND  MINING 

Rand  level.  To  facilitate  the  scheme  of  continuing  the  open 
workings  below  the  Trilby  level,  it  is  proposed  to  cut  raises  about 
30  ft.  high  at  various  points  and  to  connect  these  by  short  levels 
with  the  existing  mill  holes,  as  shown  in  Fig.  67,  or  with  raises  to 
be  cut  later  and  utilized  as  mill  holes  at  such  points  as  may  be 
deemed  advisable.  The  enormous  size  of  the  ore-bearing  terri- 
tory has  not  only  made  this  scheme  feasible,  but  highly  desirable. 

It  will  be  observed  that  at  the  end  of  the  short  level  connecting 
the  manway  from  the  Rand  level  with  the  mill  hole  is  shown  a 
small  chamber,  in  the  floor  of  which,  and  extending  out  over  the 
mill  hole,  is  a  grizzly.  Where  this  chamber  connects  with  the 
mill  hole  it  will  be  noticed  that  the  roof  is  low  —  a  mere  passage 
about  4  ft.  high,  but  which  is  the  full  width  of  the  grizzly. 
This  low  arch  acts  as  a  protection  to  the  men  working  at  the  grizzly, 
greatly  decreasing  the  danger  of  their  injury  from  large  rocks  that 
come  bounding  down  from  the  level  above  when  the  millhole  is 
empty.  As  a  matter  of  course,  it  is  desirable  to  keep  the  chute 
full,  but  owing  to  various  causes  it  is  not  always  possible  to  keep 
a  mill  hole  constantly  full  of  ore.  All  rocks  coming  down  the 
mill  hole  too  large  to  pass  the  grizzly  are  broken  by  the  men 
stationed  there,  passing  through  to  the  loading  chute  on  the  level 
below.  By  this  method  a  large  amount  of  ore  will  be  made  more 
easily  accessible  at  reduced  cost  for  mining  and  transportation. 
In  the  huge  block  of  ground  which  may  be  mined  by  open-cut 
method  are  numerous  large  stopes,  including  the  largest  in  the 
mine.  These  have  been  mined  by  the  usual  methods  employed 
in  underground  stoping,  and  the  excavations  sustained  by  means 
of  square  sets  which  have  since  been  partially  filled  with  waste. 
When,  in  the  progress  of  mining  by  the  open-cut  method,  these 
old  timbered  stopes  are  reached,  all  of  this  timber  can  be  re- 
covered, and  a  great  deal  of  it  will  in  all  probability  be  found 
in  sufficiently  good  condition  for  re-use  in  underground  stopes, 
below  the  Rand  level,  which  probably  will  never  be  mined  by 
open  cut. 

The  accompanying  engraving  (Fig.  68)  of  the  great  open  cut 
in  the  Mount  Morgan  mine,  in  Queensland,  Australia,  illustrates 
this.  Formerly  the  ore  was  extracted  by  underground  methods, 
the  stopes,  as  at  the  Yellow  Aster,  being  supported  by  square 
sets.  These  are  now  seen  exposed  in  the  sides  of  the  later  open 
excavation,  and  is  a  picture  similar  to  that  which  will  eventually 


MINING  LARGE  ORE  BODIES 


139 


140  TIMBERING   AND  MINING 

be  presented  by  the  Yellow  Aster,  or  any  other  mine,  where  open- 
cut  methods  follow  underground  stoping  and  timbering  by  square 
sets. 

At  the  Homestake  mine,  which  extends  for  10,000  feet  along 
a  gold-bearing  mineral  zone  of  prodigious  size  in  the  Black  Hills 
of  South  Dakota,  the  earliest  mining  was  by  means  of  open  cuts. 
These  cuts,  8  or  10  in  number  in  the  early  days,  have  in  some 
cases  been  extended  until  they  met,  forming  very  large  excava- 
tions, at  Lead,  Terraville  and  Central  City.  The  largest  of  these, 
however,  is  the  main  Homestake  cut  at  Lead.  This  cut,  in  the 
spring  of  1878,  was  a  hole  about  60  ft.  long,  40  ft.  wide  and  not 
over  40  ft.  deep  at  the  deepest,  up-hill  side.  This  cut  is  now  over 
1500  ft.  long,  300  to  500  ft.  wide  at  the  top,  and  in  places  more 
than  250  ft.  deep,  below  the  upper  rim.  An  enormous  tonnage 
of  ore  has  been  extracted  from  this  and  the  other  great  open 
excavations  of  the  Homestake  system,  at  a  remarkably  low  cost. 
On  the  east  or  hanging-wall  side  is  an  immense  mass  of  barren 
porphyry.  The  long-continued  excavation,  both  on  the  surface 
and  in  underground  stopes,  has  caused  acres  of  this  overburden 
to  crack  and  settle.  The  constant  movement  of  the  great  rock 
mass  has  caused  stresses  to  be  exerted  on  the  rock,  and  as  a  result 
it  is  shattered  into  millions  of  angular  blocks  of  varying  size. 
A  portion  of  the  porhpyry  exists  as  a  thick  sheet,  being  part  of  a 
laccolith  which  formerly  overlaid  the  outcroppping  ore  body. 
The  remainder  of  it  occurs  as  intrusive  dikes  coming  up  from 
below.  As  a  result  there  is  an  intermixture  of  ore  and  barren 
porphyry  near  the  surface,  both  rocks  occurring  in  large  masses. 
Owing  to  these  facts,  the  porphyry  has  been  utilized  as  filling 
for  the  immense  underground  stopes.  It  is  broken  as  above 
described,  by  the  shifting  weight  of  the  rock  mass  itself,  and  is 
constantly  on  the  move  downward  toward  the  mill  holes  which 
connect  the  great  cut  with  the  underground  workings. 

The  size  of  the  ore  body  from  the  500  ft.  level  to  the  1100  level 
is  unusual,  averaging  over  500  ft.  in  width.  Its  width  below  the 
1100  level  is  as  yet  unknown.  The  excavation  of  an  ore  body  of 
such  tremendous  size  at  minimum  cost  necessarily  requires  that 
the  several  important  factors  having  a  direct  bearing  on  expense 
be  most  favorable.  These  conditions  are  found  at  the  Homestake, 
and  the  management  of  that  great  property  has  introduced 
mining  methods,  both  at  surface  and  underground,  which  may 


MINING  LARGE  ORE  BODIES  141 

be  followed  to  great  advantage  in  many  other  places  where  con- 
ditions are  in  any  way  similar.  The  fact  of  the  intermixture  of 
ore  and  waste  in  large  blocks  in  the  upper  portion  of  the  mine 
makes  it  possible,  and  even  necessary  at  times,  to  send  all  ore, 
or  all  waste,  to  the  extent  of  a  thousand  tons,  more  or  less,  through 
any  particular  mill  hole.  For  several  days  men  in  the  cuts  will 
work  down  waste,  which,  passing  from  level  to  level,  finally  finds 
lodgement  in  some  underground  stope.  After  several  days, 
possibly,  a  large  amount  of  ore  may  have  become  available  at 
this  mill  hole,  and  then  only  ore  is  sent  down,  to  be  drawn  off  at  a 
convenient  level,  trammed  to  one  of  the  several  shafts,  hoisted, 
and  sent  to  mill.  The  condition  has  been  such  for  several  years 
past,  in  the  great  open  cuts  of  the  Homestake,  that  it  is  nothing 
uncommon  for  two  men  to  work  down  300  to  400  tons  of  ore 
daily. 

The  system  upon  which  all  open-cut  mining  work  should  be 
laid  out  and  the  work  prosecuted  should  contemplate  from  the 
beginning  the  mining  of  a  large  tonnage  of  ore  daily  with  the 
least  possible  amount  of  handling.  Topographical  situation  and 
the  character  of  the  rock  are  important  factors.  A  rock  that 
readily  breaks  up  into  comparatively  small  pieces  may  be  more 
cheaply  mined  than  that  which  is  hard  and  tough,  coming  down 
in  large  boulders,  and  requiring  subsequent  block-holing  or  bull- 
dozing. 

The  Churn-Drill  or  Jumper 

Methods  of  mining  in  open  cuts  differ  according  to  the  con- 
ditions under  which  the  work  is  done.  In  many  cases  all  the 
material  broken  is  valuable  ore.  In  others  the  ore  is  mixed  with 
waste.  Occasionally  these  —  the  ore  and  the  waste  —  are  so 
intimately  mixed  that  sorting  is  commercially  prohibited.  In 
other  instances  the  ore  and  the  waste,  though  intermingled,  both 
occur  in  such  large  masses  that  each  may  be  mined  separately, 
as  in  the  Homestake  cuts,  as  previously  explained.  Again,  ore 
and  waste  are  not  intimately  mixed,  but  occur  in  such  manner 
that  by  blasting  carefully  the  two  may  be  kept  separate  to  a  great 
extent.  Where  this  latter  condition  prevails,  the  holes  are^ 
drilled  in  the  usual  manner  by  hand,  or  with  machines.  The 
drill  holes  may  then  be  from  4  to  6  ft.  deep,  charged  and  fired 
in  the  usual  way.  Where,  however,  there  is  no  need  of  such 


142  TIMBERING   AND  MINING 

careful  procedure,  and  there  is  no  objection  to  breaking  down 
hundreds,  or  even  thousands,  of  tons  at  a  single  round  of  holes, 
the  churn-drill  or  jumper,  as  it  is  often  called  by  English  miners, 
can  be  employed  to  great  advantage.  This  method  of  drilling 
holes  for  blasting  may  be  employed  with  equal  usefulness  in 
quarries  where  the  rock  is  being  broken  for  macadam,  concrete, 
or  other  similar  purposes,  and  where  the  shape  or  size  of  the  rock 
broken  is  of  no  consequence,  the  chief  thing  being  the  amount 
that  may  be  thrown  down  with  a  single  shot. 

The  following  is  a  description  of  the  method  employed  where 
the  rock  was  tough,  but  not  particularly  hard.  The  holes  were 
started  by  hand-drills  of  the  usual  kind,  the  bits  being  2J-  in. 
wide.  These  holes  were  drilled  5  ft.  deep  with  double-hand 
hammer,  when  the  drillers  moved  on  to  another  place  and  started 
a  second  hole.  One  man  with  a  12-ft.  jumper  (churn-drill), 
made  of  1J  in.  gas-pipe  with  drill-bits  welded  to  eacli  end,  began 
to  deepen  the  5-ft.  hole.  When  deep  enough,  a  16-ft.  drill  was 
substituted  for  the  12-ft.  drill  and  two  men  then  handled  the  drill. 
The  third  drill  was  20  ft.  long,  and  when  this  came  into  use  three 
men  were  put  on  the  drill.  Following  the  20-ft.  drill  came  the 
last  one,  from  24  to  26  ft.  in  length.  With  the  longest  drill  three 
men  still  constituted  the  drilling  crew.  The  widest  bit  on  the 
churn-drill  was  If  in.,  the  narrowest  If  in. 

The  bits  should  be  forged  strong  —  it  is  a  mistake  to  make 
them  too  thin,  for  the  corners  are  likely  to  be  broken  off.  The 
temper  must  be  low  —  dark  straw  color  to  blue  —  or  the  corners 
may  check  and  break,  and  it  is  difficult  to  remove  broken  pieces 
of  bits  from  a  deep  hole.  The  best  way  to  get  them  out  is  with  a 
strong  bar  magnet,  attached  to  a  cord,  which  usually  secures  the 
desired  fragment  in  a  moment.  Miners  often  waste  much  time  in 
"spooning"  after  a  bit  of  broken  drill. 

Clean  the  holes  down  to  4  ft.  with  the  scraper.  Deeper  holes 
should  be  cleaned  with  eye-bars  of  |-in.  iron.  A  strip  of  cloth 
or  rope-yarn  should  be  run  through  the  eye.  This,  if  churned 
up  and  down  in  the  hole,  becomes  loaded  with  the  muck,  which  is 
then  drawn  out  of  the  hole  and  the  superfluous  part  stripped  off 
by  running  the  rag  between  thumb  and  fingers.  The  process  is 
repeated  until  most  of  the  muck  has  been  removed,  when  drilling 
may  be  resumed.  The  swab  of  rope-yarn  must  not  be  too  long, 
or  it  may  double  up  and  cause  trouble  by  jamming  in  the  hole. 


MINING  LARGE  ORE  BODIES  143 

When  the  hole  is  finished  to  the  desired  depth,  the  chamber 
is  started  by  shooting  two  sticks  of  40  per  cent.,  followed  by  6  or 
8  sticks  of  No.  1  (70  per  cent.)  dynamite;  third  time  by  12  to  15 
sticks  No.  1,  and  the  fourth  time  by  20  or  more  sticks  of  the  same. 
The  succession  of  these  operations,  and  amount  of  powder  em- 
ployed and  number  of  times,  must  be  determined  by  the  character 
of  the  ground  and  the  way  it  breaks,  as  shown  by  actual  experi- 
ence. In  some  fairly  easy  ground  two  or  three  rounds  of  20 
sticks  of  No.  1,  after  the  preliminary  shots  with  Nos.  1  and  2,  are 
sufficient,  but  in  hard  and  tough  ground  it  may  be  well  to  shoot 
3  to  5  times  with  20  or  more  sticks  of  No.  1,  before  the  chamber 
is  sufficiently  large  to  receive  the  necessary  amount  of  "low" 
dynamite  or  black  powder. 

When  beginning  the  operation  of  "springing  the  hole,"  put 
down  two  sticks  of  No.  2  and  follow  it  with  the  tamping  stick 
to  be  sure  it  is  at  the  bottom  of  the  hole.  Insert  the  detonator 
in  a  full  stick  of  powder.  Use  a  30-in.  fuse.  Spit  the  fuse,  allow 
it  to  burn  about  two  inches,  and  then  close  the  end  by  pressing 
the  burned  portion  with  the  fingers.  This  has  a  tendency  to 
exclude  any  water  that  may  seep  into  the  fuse  and  extinguish 
the  fire.  Drop  the  fuse  and  primer  into  the  hole  and  get  out  of 
the  way  of  small  rocks  that  may  be  blown  up  out  of  the  hole. 
After  springing  the  hole,  pour  water  into  it  to  extinguish  any  fire 
in  any  piece  of  fuse  tape,  before  pouring  in  black  powder  or  low 
dynamite.  In  a  20-ft.  hole  that  has  been  properly  chambered 
it  is  customary  to  use  200  Ib.  of  Judson  5  per  cent." low"  powder. 
It  comes  loose  in  50-lb.  cases.  This  quantity  may  or  may  not 
be  sufficient.  Experiment  only  can  determine  this. 

The  distance  that  a  series  of  holes  may  be  drilled  back  from 
the  collar  varies  with  the  rock.  In  some  cases  10  to  12  ft.  is  as 
heavy  a  burden  as  may  safely  be  placed  on  the  hole;  in  other 
cases  it  may  be  as  much  as  18  to  20  ft.  back  from  the  face.  A 
single  hole  drilled  20  ft.  deep  and  20  ft.  back  from  a  vertical 
face  is  theoretically  calculated  to  break  about  600  tons  of  ordinary 
ore,  but  a  series  of  four  holes  placed  30  ft.  apart,  20  ft.  back  from 
the  face  and  drilled  20  ft.  deep,  is  likely,  in  fair  ground,  to  break 
from  4000  to  6000  tons  of  rock  —  a  very  much  higher  average 
than  can  be  accomplished  with  a  single  hole  20  ft.  deep  with 
a  20-ft.  burden.  Moreover,  a  series  of  such  holes  is  more  likely  to 
accomplish  desired  results  than  a  single  hole.  Churn-drilling  is 


144  TIMBERING   AND  MINING 

recommended  as  a  cheap  method  of  breaking  rock  where  the  con- 
ditions are  suited  to  this  class  of  mining  practice.  It  is  an  in- 
expensive method  where  the  conditions  are  right  and  when  the 
work  is  done  by  experienced  men  who  are  not  afraid  to  work. 
At  mines  where  there  is  a  proper  air-compressing  plant  and  good 
drills,  the  holes  may  be  drilled  by  machine  to  a  depth  of  10  ft. 
and  even  more,  to  advantage,  before  employing  the  churn-drill, 
and  with  suitable  machines  the  holes  may  be  drilled  to  the  depth 
of  20  ft.  or  more.  Such  machines,  however,  are  larger  than  those 
ordinarily  employed  in  metal  mining.  The  question  of  economy 
of  machines  over  hand  work  must  be  determined  by  the  manage- 
ment. In  churn-drilling  the  personal  equation  is  a  very  im- 
portant factor. 

The  Steam  Shovel  in  Open  Cuts 

In  no  part  of  the  world  is  mining  carried  on  on  a  larger  scale 
or  at  less  expense  per  ton  than  in  the  iron  mining  regions  of  Min- 
nesota and  Michigan.  In  these  districts  many  millions  of  tons 
of  ore  are  mined  annually  at  a  surprisingly  low  cost.  Both  sur- 
face (open  cut)  and  underground  methods  of  mining  are  in  vogue, 
but  by  far  the  larger  part  of  the  ore  is  mined  in  the  open,  in  which 
the  steam-shovel  is  a  most  important  factor.  The  procedure 
in  the  Mesabi  Range  is  simple.  The  glacial  drift,  or  "over- 
burden," is  stripped  from  the  ore  with  steam-shovels.  The  thick- 
ness of  the  drift  removed  may  be  only  a  few  feet,  or  as  much  as 
85  ft.  The  average  is  between  20  and  40  ft.  Among  mining 
men  the  expression  is  common  that  it  pays  to  strip  as  great  a 
thickness  of  drift  as  there  is  ore  beneath.  However,  factors 
other  than  thickness  of  the  ore  beneath  frequently  determine 
the  amount  of  drift  that  it  is  advisable  to.  attempt  to  remove. 
The  total  amount  of  drift  that  has  had  to  be  removed  from  some 
of  the  large  deposits  is  very  great,  numbered  by  millions  of  cubic 
yards.  When  the  surface  of  the  ore,  or  part  of  it,  is  stripped, 
standard-gage  railroad  tracks  are  built  out  on  the  ore  deposit 
and  steam-shovels  make  a  cut  through  the  ore.  The  ore  of  the 
Mesabi  range  is  soft  and  may  be  mined  in  this  manner  by  steam- 
shovel.  In  the  first  cut  the  ore  is  either  thrown  to  one  side,  or 
is  loaded  directly  on  to  cars  on  a  parallel  track.  After  the  first 
cut  the  shovel  is  set  over  against  the  bank  and  another  slice 
taken  off,  and  loaded  on  to  cars  run  in  the  cut  already  made. 


MINING  LARGE  ORE  BODIES  145 

When,  by  a  series  of  cuts  or  slices,  the  bank  or  bench  is  carried 
back  far  enough,  work  is  begun  as  before  on  a  lower  level,  and  in 
time  this  is  followed  by  cuts  on  a  third  and  fourth  level,  carving 
the  deposit  into  a  series  of  banks  or  terraces,  at  several  levels, 
against  any  or  all  of  which  steam-shovels  may  work,  giving 
access  to  a  great  variety  of  ores  and  making  possible  a  large  out- 
put in  a  short  time.  In  some  of  the  mines  the  cut  is  started  near 
the  middle  and  the  work  is  carried  forward  toward  each  side.  In 
others  the  first  cut  is  made  in  spiral  form,  leaving  a  bank  in  the 
middle,  so  that  subsequent  cutting  goes  on  both  toward  the  center 
and  toward  the  periphery  of  the  deposit  at  the  same  time.  While 
the  ore  is  soft,  it  is  usually  too  compact  to  handle  economically 
without  blasting,  so  a  small  amount  of  this  is  done  for  the  purpose 
of  shaking  up  the  ore.  The  system  of  trackage  varies  greatly 
in  the  several  mines,  depending  upon  the  distribution  and  charac- 
ter of  the  ores  and  the  shape  of  the  deposit.  The  mill  hole  is  also 
made  use  of  in  some  of  these  mines,  but  it  is  a  method  not  gen- 
erally adopted  in  the  Mesabi  region. 

The  glacial  drift  is  removed  as  in  an  open-cut  steam-shovel 
mine.  A  shaft  is  sunk  in  the  adjacent  wall  rock  to  the  level  of 
the  bottom  of  the  deposit,  and  drifts  or  cross-cuts  are  run  out 
through  the  ore.  Raises  or  chutes  without  timber  are  sent  up 
from  the  cross-cuts  or  drifts.  By  blasting,  the  ore  is  then  loosened 
at  the  surface  and  pushed  into  the  mill  holes  by  men.  It  is  drawn 
into  cars  stationed  at  the  chutes,  trammed  to  the  shaft,  and  hoisted. 
Another  practice  is  to  dump  the  ore  directly  into  the  mill  holes 
by  means  of  steam-shovels  instead  of  by  manual  labor.  This 
method  has  been  found  satisfactory. 

In  a  comparison  of  methods  —  steam-shovels  operating  along 
benches  or  terraces,  the  mill-hole  system,  and  underground 
mining,  the  advantage  in  cost  per  ton  lies  with  the  steam-shovel. 
By  that  method  all  of  the  ore  may  be  recovered,  the  work  may 
be  performed  largely  or  wholly  in  daylight,  no  timber  is  required, 
and  the  number  of  men  necessary  for  the  handling  of  a  large 
tonnage  within  stated  time  is  reduced  to  a  minimum. 

So  successful  has  the  steam-shovel  in  open  cuts  become  that 
the  method  has  been  extensively  introduced  in  the  metal  mines 
of  the  West  and  abroad. 

The  first  to  employ  the  steam-shovel  in  a  metal  mine  in  the 
West  was  the  Granby  Copper  Company,  in  British  Columbia. 


146 


TIMBERING  AND  MINING 


MINING  LARGE  ORE  BODIES  147 

This  was  several  years  ago.  Since  then  the  steam-shovel  has 
been  introduced  with  success  at  Bingham,  Utah;  at  the  Cactus 
mine,  in  Beaver  County,  Utah;  at  Mount  Lyell,  Tasmania;  at  the 
great  copper  mines  of  the  Ely  district,  Nevada  (see  Fig.  69), 
and  elsewhere,  and  there  are  scores  of  other  places  where  they 
may  be  employed  to  excellent  advantage,  particularly  in  the 
removal  of  overburden  from  ore  deposits  which  may  then  be 
mined  by  steam-shovels,  or  by  mill-hole  system. 


CHAPTER  XIV 

THE  OVERHAND  AND  UNDERHAND  METHODS  OF 
STOPING  VEINS 

THE  removal  of  ore  from  veins  or  deposits  in  underground 
workings  is  commonly  known  as  sloping,  and  the  excavations 
made  in  this  manner  are  called  stopes  (originally  steps),  the  ore 
usually  being  removed  in  horizontal  slices,  leaving  a  series  of 
"steps"  in  the  vein.  Stopes  vary  greatly  in  size  and  shape, 
depending  partly  on  the  position  and  form  of  the  ore  deposit 
and  partly  on  the  character  of  the  ore  or  the  surrounding  country 
rock.  A  vein  of  hard  ore  in  firm  walls  can  be  stoped  in  a  very 
different  manner  from  a  soft  and  crumbling  vein,  or  one  where  the 
walls  are  soft  or  otherwise  insecure.  The  size  of  the  vein  or 
deposit  and  the  angle  or  pitch  of  its  walls  will  also  often  have  a 
very  important  bearing  on  the  method  of  stoping  adopted. 

Stoping  is  of  two  kinds,  distinguished  as  underhand  and  over- 
hand. Underhand  stoping,  which  is  the  method  of  removing 
ore  by  downward  steps,  is  almost  exclusively  confined  to  veins 
of  small  width  and  was  at  one  time  very  generally  practised,  but 
is  now  only  rarely  seen,  and  is  then  usually  the  result  of  an  en- 
deavor to  remove  ore  quickly  from  a  vein  without  the  necessity 
of  first  doing  the  development  work  otherwise  necessary  to  get 
under  the  ore  body.  It  is  an  expensive  method  and  is  attended 
by  many  disadvantages.  All  the  water  coming  out  of  the  vein 
or  walls  runs  down  the  several  terraces  of  the  stope,  keeping  it 
wet  and  mucky.  All  ore  has  to  be  handled  with  greater  care  and 
often  picked  by  hand.  Underhand  stoping  may  be  justified  in 
small  veins  of  rich  ore,  and  where  the  geological  conditions  in- 
dicate that  the  ore  shoot  does  not  go  to  great  depth,  but  generally 
speaking  underhand  stoping  is  inadvisable.  Several  years  ago 
the  writer  visited  a  mine  and,  accompanying  the  superintendent 
down  the  shaft,  found  the  first  level  opened  125  ft.  from  the  sur- 
face. Beneath  the  level  an  underhand  stope  had  been  started 
fully  20  ft.  wide  and  about  40  ft.  long.  It  was  being  timbered  in 

148 


METHOD   OF  STOPING   VEINS  149 

square-sets.  Having  never  seen  anything  like  this  previously, 
the  superintendent  was  asked  why  this  method  of  mining  had 
been  attempted.  His  reply  was  that  he  had  a  smelter  of  100  tons 
capacity  to  supply.  This  was  a  desperate  effort  to  meet  the  re- 
quirements of  a  metallurgical  plant  which  had  indiscreetly  been 
built  before  the  mine  had  been  sufficiently  developed  to  warrant 
a  smelter.  Within  30  days  from  the  date  of  the  visit  above  men- 
tioned both  smelter  and  mine  were  closed. 

Underhand  stoping  was  formerly  very  popular  with  Cornish 
miners,  for  various  reasons,  but  is  less  in  vogue  now,  as  the  more 
direct  and  economical  method  of  overhand  stoping  is  almost 
exclusively  practised.  Underhand  stoping  may,  however,  be 
proper  in  a  few  instances  where  it  is  desirable  to  remove  ore  from 
the  surface  downward  for  a  few  feet,  say  20  to  40  ft.,  and  where 
the  hoisting  is  to  be  done  by  means  of  a  windlass  or  whim.  A 
shaft  is  sunk  to  the  depth  to  which  it  is  intended  to  carry  stoping, 
or  a  little  deeper,  in  order  that  a  sump  may  be  formed  at  the 
bottom  to  collect  the  drainage,  if  there  be  any  water  present. 
The  stoping  then  begins  by  mining  a  shallow  open  cut  about 
8  or  9  ft.  deep,  along  the  surface,  carrying  the  work  in  each  direc- 
tion from  the  shaft  along  the  vein.  The  ore  removed  is  taken 
in  a  wheelbarrow  to  the  shaft  and  dumped  on  an  apron,  which 
delivers  it  to  the  bucket,  or  the  bucket  is  hauled  in  onto  the  level 
and  the  ore  shoveled  directly  into  it  from  the  accumulated  pile. 
When  the  work  in  this  cut  or  trench  has  advanced  20  ft.,  or  there- 
abouts, a  second  cut  may  be  started  8  or  9  ft.  lower,  and  carried 
forward  in  the  same  manner.  If  the  first  cut  has  not  been  carried 
to  the  limit  of  the  ore  shoot,  stulls  must  be  placed  at  the  level  of 
the  floor  of  stope  No.  1,  and  these  covered  with  lagging,  forming 
a  strong  platform  over  which  the  miners  working  in  the  upper 
cut  may  carry  their  ore,  and  on  which  may  be  accumulated  any 
waste  or  other  debris  resulting  from  mining  in  stope  No.  1.  When 
stope  No.  2  has  been  advanced  sufficiently,  stope  No.  3  may  like- 
wise be  started,  and  later  No.  4,  each  being  driven  from  the  shaft 
toward  the  limits  of  the  ore  shoot.  It  is  only  in  rare  cases  that 
this  method  of  mining  is  seen  in  the  Western  United  States,  as  it 
involves  too  much  work  for  the  results  accomplished,  and  it  is 
only  in  exceptional  cases  that  its  adoption  may  be  recommended. 

In  Cornish  mines,  where  underhand  stoping  is  practised,  the 
usual  method  is  to  sink  the  shaft,  drive  several  levels,  and  connect 


150  TIMBERING  AND  MINING 

these  several  levels  with  a  series  of  raises,  some  of  which  are 
utilized  as  ore  passes.  The  ore  is  stoped  by  the  underhand 
method,  conveyed  from  the  several  working  faces  to  the  nearest 
mill  hole,  into  which  it  is  dumped,  to  be  drawn  off  into  a  car 
through  a  chute  built  at  the  foot  of  the  raise.  The  mill  hole  is 
sometimes  cribbed  and  sometimes  planked,  open  places  being 
left  at  each  floor  so  that  the  ore  may  be  dumped  into  the  mill 
hole.  The  ore  must  be  drawn  off  about  as  fast  as  it  is  thrown 
into  the  mill  hole,  as  it  cannot  be  allowed  to  accumulate  to  a 
higher  level  in  the  mill  hole  than  the  lowest  working  floor  in  that 
stope.  Overhand  stoping  is  the  most  commonly  practised 
throughout  the  metal  mining  regions  of  the  world.  A  treatise 
on  stoping  is  in  itself  a  large  undertaking,  and  we  have  no  inten- 
tion of  describing  its  many  variations,  referring  only  to  those 
methods  most  commonly  in  use  and  which  have  been  found  to 
be  the  most  satisfactory. 

The  methods  of  stoping  may  be  divided  into  several  kinds: 
Stoping  with  the  use  of  simple  stulls  to  support  the  walls;  stop- 
ing without  timbers,  by  allowing  two-thirds  of  the  ore  to  remain 
in  the  stope  until  the  ore  is  all  removed,  when  it  may  all  be  drawn 
off;  stoping  by  means  of  the  square-set  system  of  timbers;  by 
room-and-pillar  method;  by  the  caving  system;  or  by  some  other 
one  of  several  methods  not  commonly  practised  because  they  have 
been  evolved  to  meet  peculiar  or  unusual  conditions  not  usually 
found  in  mines.  The  simplest  method  of  stoping  by  the  overhand 
system  is  in  the  rem'oval  of  a  vein  of  clean  ore,  where  the  vein 
is  of  moderate  width  —  say  less  than  16  ft.  This  is  accomplished 
in  several  -ways.  In  former  years  it  was  the  practice  to  drive  a 
level  along  the  vein,  placing  heavy  drift  sets,  if  the  walls  and 
character  of  the  vein  demanded  it,  and  laying  thick  lagging  on 
the  caps.  The  ore  overhead  was  then  broken  down  onto  the 
lagging  and  shoveled  into  chutes  built  at  intervals  —  usually 
of  30  ft.  —  along  the  level.  As  stoping  proceeded  upward, 
stulls  were  placed  and  these  were  covered  with  platforms  on 
which  the  miners  stood  when  at  work.  The  ore  was  sent  down 
to  the  chutes  on  the  level  through  ore  passes  (sections  in  the  stope 
cribbed  with  timbers)  and  drawn  off  into  cars.  This  method 
eventually  leaves  a  large,  open  excavation  in  the  mine,  the  ore 
all  having  been  drawn  off,  and  only  the  stulls  remaining  to  sup- 
port the  walls,  the  platforms  of  lagging  having  been  removed. 


METHOD   OF   STOPING   VEINS 


151 


Fig.  70  illustrates  the  method  of  placing  stalls  in  a  stope,  the 
engraving  representing  one  that  has  been  carried  up  to  the  sur- 
face from  below. 

In  many  veins  of  high  inclination  the  conditions  are  such  that 


FIG.  70.  —  An  Open  Stope  in  a  California  Mine 

stoping  may  be  most  conveniently  and  economically  carried  on 
by  breaking  all  the  ground  in  the  stope,  drawing  off  only  about 
one-third,  or  only  so  much  as  will  permit  the  miners  head  room 
while  standing  on  the  broken  ore,  to  continue  the  work  of  mining 
overhead.  When  this  is  done,  the  ore  is  drawn  off  through 


152  TIMBERING   AND   MINING 

chutes  built  at  intervals  of  30  to  40  ft.  along  the  level.  On  the 
level,  drift  sets  may  be  put  in,  covered  with  heavy  lagging,  or, 
if  the  walls  be  hard  and  firm,  stulls  only  need  be  employed.  The 
loading  chutes  are  built  in  the  usual  manner,  either  attached  to 
upright  posts  or  built  in  between  two  stulls.  As  the  ore  is 
broken  down,  the  miners  break  up  all  large  pieces,  either  by  bull- 
dozing or  block-holing,  and  finally,  if  necessary,  with  hammers, 
until  no  piece  remains  that  will  not  pass  through  the  loading 
chute.  All  the  rock  broken  in  the  stope  may  be  drawn  off  through 
the  chutes  without  shoveling,  except  that  which  remains  on  the 
lagging  of  the  gangway  sets  when  the  "  angle  of  convenience"  has 
been  reached  near  the  bottom.  When  the  rock  ceases  to  run  by 
gravitation  to  the  chutes,  men  go  into  the  stope  and  shovel  the 
ore  lying  on  the  lagging  into  the  chutes.  If  this  be  too  dangerous 
or  for  any  reason  impracticable,  an  intermediate  chute  may  be 
put  in  midway  between  two  regular  chutes  and  most  of  the  ore 
recovered.  At  each  end  of  every  such  stope  must  be  arranged 
manways  for  the  entry  and  exit  of  men  and  for  the  purpose  of 
maintaining  a  free  circulation  of  air.  But  one  of  these  openings 
need  be  provided  with  ladders,  though  in  many  mines  it  is  the 
custom  to  hang  a  rope  from  a  stull  in  the  other  in  anticipation 
of  an  accident  to  the  main  manway.  The  above  assumes  that 
the  vein  consists  of  clean  ore,  or  that  the  waste  is  present  in  such 
small  amount  as  to  make  it  a  matter  of  relatively  small  conse- 
quence. 

.  Very  often  waste  occurs  with  the  ore  to  such  an  extent  as  to 
form  a  very  considerable  part  of  the  vein  material,  and  often,  too, 
the  walls  are  not  as  firm  as  could  be  desired,  large  slabs  being 
loosened  and  falling  upon  the  broken  ore.  These  must  either 
be  supported  with  stulls  or  taken  down  to  insure  the  safety  of  the 
miners.  When  such  conditions  obtain  the  ore  must  be  sorted 
from  the  waste  and  sent  down  to  the  loading  chutes  on  the  level 
below,  through  cribbed  mill  holes  that  are  carried  up  in  the-  stope 
as  the  work  progresses  upward.  It  is  the  best  practice  to  keep 
these  mill  holes  full  of  ore,  even  if  the  amount  broken  is  com- 
paratively small.  By  doing  so  the  danger  of  men  falling  into 
them  is  obviated,  and  no  large  pieces  of  waste  can  drop  into  a 
position  where  it  is  disadvantageous  to  break  it  up.  Often, 
while  there  is  considerable  waste  encountered  in  the  vein,  or  the 
waste  from  the  walls  is  so  troublesome  that  the  method  of  mining 


METHOD   OF   STOPING   VEINS  153 

just  described  is  adopted,  still  the  amount  of  waste  is  not  sufficient 
to  keep  the  stope  filled  up  close  enough  to  the  back  to  keep  the 
miners  within  reach  of  the  ore.  In  such  cases  it  may  be  expedient 
to  break  enough  of  the  walls  to  supply  the  necessary  filling.  As  a 
matter  of  course,  the  breaking  of  all  the  ore  and  allowing  it  to 
remain  in  the  stope  has  its  advantages  over  this  latter  method, 
which  requires  sorting,  cribbed  mill  holes  and  other  expenditures 
of  labor  and  money  that  in  the  former  case  are  unnecessary,  but 
we  have  not  always  either  clean  ore  or  firm  walls.  Which  of  the 
two  systems  is  adopted  must  be  determined  by  the  judgment 
of  the  superintendent.  In  some  instances  where  waste  occurs, 
but  is  not  particularly  abundant,  the  first  method  is  employed, 
the  greater  part  of  the  waste  —  the  larger  pieces  —  being  thrown 
out  by  hand  at  the  loading  chute,  at  the  surface  chute,  at  the 
rock-breaker,  or  wherever  it  may  show  itself.  Not  infrequently 
conditions  in  different  parts  of  the  same  mine  are  so  unlike  that 
the  methods  employed  in  the  various  stopes  differ,  according  to 
the  existing  conditions. 


CHAPTER  XV 

UNUSUAL   METHODS   OF   STOPING   ENFORCED   BY 
SCARCITY   OF  TIMBER 

IN  desert  regions  the  scarcity  of  timber  is  an  important  feature 
in  mining  economics  and  has  led  to  the  introduction  of  unusual 
methods  of  ore  recovery.  These  methods  may  also  be  employed 
in  other  mines  where  timber  is  not  scarce,  and  may  in  some  cases 
be  found  to  possess  advantages  over  old  methods. 

One  of  the  most  practical  and  satisfactory  methods  of  stoping 
in  veins  of  normal  width  —  5  to  20  ft.  —  is  to  drive  a  gangway 
in  the  vein,  put  in  raises  at  every  30  ft.  and  at  a  height  of  10  to 
20  ft.  above  the  back  of  the  main  gangway  (depending  on  the  size, 
character  and  condition  of  the  veins,  and  its  walls),  and  to  open 
a  level  by  driving  an  upper  drift,  from  which  stoping  proceeds 
upward.  This  leaves  a  solid  block  of  ore  between  the  back  of 
the  main  gangway  and  the  floor  of  the  stope.  Of  course,  this 
method  anticipates  that  the  vein  is  firm  and  that  no  timber  is 
required  to  support  the  back  of  the  main  gangway.  This  block 
of  ore  is  only  penetrated  by  the  raises  cut  for  ore  passes  and 
manways.  The  ore  is  stoped  in  the  usual  manner  and  only 
enough  drawn  off  to*  keep  the  miners  within  reach  of  the  back  of 
the  stope.  The  mill  holes  are  those  cut  through  the  block  of  ore, 
each  being  provided  with  a  chute  in  the  gangway  below.  The 
end  raises  are  maintained  as  manways  and  for  ventilation,  and 
may  require  some  timbering. 

The  Black  Mountain  mine,  at  Cerro  Prieto,  Sonora,  Mexico, 
is  being  worked  in  this  manner,  very  similar  to  the  method  em- 
ployed in  some  parts  of  the  Treadwell  mine,  Douglas  Island, 
Alaska.  The  mines 'of  Zaruma,  Ecuador,  also  afford  an  interest- 
ing example  of  special  methods,  described  by  Mr.  J.  R.  Finlay 
in  the  "Transactions  of  the  American  Institute  of  Mining  Engi- 
neers" (Vol.  XXX,  page  248). 

The  method  followed  there  was  suggested  by  the  practice  at 
an  iron  mine  at  Tower,  Minnesota.  The  excellence  of  the  scheme 

154 


SCARCITY  OF  TIMBER  155 

led  to  the  adoption  of  a  modification  of  the  idea  at  the  Eagle- 
Shawmut  mine,  near  Chinese,  California,  by  the  superintendent, 
Mr.  Charles  Uren.  Wages  at  Zaruma  are  50  cents  a  day  (gold) 
for  common  labor;  60  cents  to  $1  for  native  miners;  $1  for  Jamaica 
negroes;  $2  for  Italian  miners.  American  mechanics  and  miners 
receive  $140  per  month  and  upward. 

Mr  Finlay  thus  describes  the  method  of  mining  introduced  by 
him  at  Zaruma:  "The  first  ore  body  opened  by  the  present  com- 
pany was  on  the  '  Abundencia '  vein.  The  ore  was  not  very  hard 
except  in  spots,  and  was  accompanied  by  an  exceedingly  soft  and 
treacherous  foot-wall.  It  was  evident  that,  whether  timber 
were  used  in  the  stopes  or  not,  they  would  have  to  be  filled  with 
rock.  The  only  other  alternative  was  to  slice  the  body  from  the 
top  downward.  The  latter  method  may  yet  have  to  be  adopted 
near  the  surface,  but  it  involves  great  difficulty  in  keeping  open 
the  raises,  which  are  necessary,  both  for  ventilation  and  for  fur- 
nishing future  rock-filling  for  the  lower  levels.  The  method  of 
mining  actually  adopted  was  essentially  the  filling  system  used 
at  the  hard  ore  mines  of  the  Minnesota  Iron  Co.,  at  Tower,  Minne- 
apolis, with  the  exception  that  the  fills,  and  of  course  the  stopes, 
were  made  sloping  instead  of  horizontal.  In  the  first  ore  body 
attacked,  three  raises,  each  from-  200  to  300  ft.  high,  were  made 
along  the  foot-wall  to  the  surface,  coming  out  at  the  bottom  of 
the  deep  open  cut  of  the  old  Spaniards,  from  the  sides  of  which 
any  quantity  of  rock  could  be  milled  down  into  the  mine  at  a 
nominal  cost.  These  three  raises  were  130  ft.  apart.  The  tunnel 
was  run,  not  in  the  vein  itself,  but  at  a  safe  distance  (about  20  ft.) 
in  the  foot-wall.  Cross-cuts  were  driven  to  the  vein  every  65  ft., 
so  that  there  was  an  entrance  to  the  stopes  at  each  of  the  raises, 
and  also  midway  between  them.  Stoping  began  by  cutting  out 
the  vein  to  its  full  width,  and  about  eight  feet  high,  on  the  main 
level.  Tracks  were  laid  in  the  cross-cuts  between  the  raises. 
When  the  bottom  was  cut  off,  the  vein  was  also  beaten  away  as 
far  as  could  safely  be  done  at  the  bottom  of  the  raises.  Then  a 
lot  of  waste  rock  was  thrown  down  each  raise,  which  nearly  filled 
the  openings  thus  made.  This  filling  was  allowed  to  lie  nearly 
at  the  angle  of  repose,  and  upon  the  sloping  sides  of  the  pile  slabs 
were  laid,  to  keep  the  ore  from  mixing  with  the  rock.  Then 
another  slice  was  taken  off  as  high  as  safety  permitted,  and  the 
operation  was  repeated.  Cribbed  manways  were,  of  course, 


156 


TIMBERING   AND   MINING 


puncuo  ucujcg 


SCARCITY   OF  TIMBER  157 

carried  up  through  the  filling,  to  preserve  the  raises  for  future 
use.  The  slopes  on  each  side  of  the  filling  raises  soon  came  to- 
gether, half  way  between  the  raises,  or  at  the  intermediate  cross- 
cut. At  these  points  chutes  were  put  in,  and  carried  upward  by 
cribbing  as  the  stoping  and  filling  proceeded.  Fig.  71  illustrates 
the  mining  method  adopted  at  Zaruma. 

"This  method  of  mining  has  the  following  advantages:  (1)  It 
requires  but  little  timber  —  an  important  consideration  where 
timber  is  scarce.  (2)  It  allows  of  filling  and  tramming  without 
re-handling,  and,  therefore,  at  a  minimum  expense.  (3)  It 
allows  the  fill  to  be  made  very  close  to  the  back,  because  it  is 
not  necessary  to  leave  standing  room  on  the  slope  for  men  to 
stow  the  dirt.  This  is  a  very  important  consideration  where  the 
walls  are  soft. 

"The  system  works  well.  The  slope-filling  feature  of  it  was 
invented  by  Mr.  Thomas  Huddlestone,  mining  captain  on  the 
property.  The  ore  costs,  for  labor,  supplies  and  superintendence, 
about  70  cents  a  ton,  delivered  at  mill.  This  figure  relates  only 
to  the  operation  of  the  stopes,  and  does  not  include  the  large 
amount  of  development  work  done." 

It  is  not  quite  clear  what  keeps  the  slabs  in  position  on  the 
sloping  sides  of  the  fill,  nor  how  the  miners  find  a  secure  footing 
by  this  method. 


CHAPTER  XVI 

STOPING   IN   FLAT   OR   LOW-LYING   VEINS 

IN  veins  which  lie  quite  flat,  the  character  of  the  ore  and  that 
of  the  overlying  wall  must  necessarily  determine  the  method 
of  mining  that  may  be  adopted  with  safety  and  economy.  In 
some  localities  flat  deposits  of  ore  lie  at  the  surface,  or  have  very 
little  overburden  that  must  be  removed.  These  conditions 
afford  an  opportunity  for  very  cheap  mining.  In  the  Black 
Hills  of  South  Dakota  are  numerous  deposits  of  this  character. 
The  ore  occurs  in  and  on  the  Cambrian  quartzites,  and  in  a  number 
of  cases  erosion  has  removed  the  later  deposits  and  the  bed  of  ore 
lies  uncovered  at  the  surface.  Among  the  several  mines  of  this 
type,  that  at  the  Wasp  No.  2  mine,  on  Yellow  Creek,  is  perhaps 
the  most  noted  example.  There  open-cutting  in  these  flat  veins 
has  been  reduced  to  a  science.  The  practice  there  is  usually  to 
drill  a  single  hole  from  the  surface  to  the  bottom  of  the  ore  bed, 
about  20  ft.  This  hole  is  set  back  30  to  40  ft.  from  the  face.  It 
is  chambered  repeatedly,  as  described  under  the  head  of  churn- 
drilling.  When,  in  the  judgment  of  the  foreman,  the  chamber 
is  sufficiently  large,  several  hundred  pounds  of  black  powder 
are  charged  and  the  blast  fired.  The  result  is  that  from  5000  to 
6000  tons  of  ore  are  lifted  slightly,  settling  back  into  position 
again.  None  but  a  close  observer  would  notice  any  material 
change  in  the  appearance  of  the  ore  after  the  "big  shot"  had 
been  fired,  but  the  entire  mass  is  thoroughly  shattered,  and  for 
a  month  the  miners  have  only  to  shovel  away  the  broken  rock, 
the  larger  pieces  being  bulldozed  or  block-holed. 

Where  the  flat  veins  extend  beneath  a  mountain,  all  oppor- 
tunity for  adopting  the  method  just  described  is  lost,  and  the 
vein  must  be  attacked  in  a  different  manner.  The  system  of 
mining  will  in  such  cases  be  very  largely  influenced  by  the  charac- 
ter of  the  ore  and  of  the  walls.  Where  the  vein  is  thin  (a  foot  or 
two),  usually  very  little  timber  is  required,  the  waste  rock  filling 

158 


STOPING  IN  FLAT  OR  LOW-LYING   VEINS  159 

the  entire  space  behind  the  miner.  Where  the  mineral  deposit 
is  thicker  and  timber  is  necessary,  various  methods  are  pursued. 
Some  ground  stands  well  by  simply  leaving  pillars  of  mineral. 
In  other  cases  a  series  of  upright  posts  and  breasting  caps  will 
sustain  the  roof,  the  posts  being  placed  in  rows  directly  back  of 
the  workmen  and  as  close  to  the  face  as  necessity  demands. 
The  foot  of  the  post  rests  either  directly  on  the  rock  floor  or  upon 
a  block  of  wood  or  piece  of  heavy  plank.  The  posts  are  forced 
into  position  by  driving  them  up  with  heavy  hammers.  Care 
must  be  taken  that  these  posts  are  so  placed  as  to  receive  the 
weight  of  the  roof  directly,  and  not  at  an  angle.  These  timbers 
are  set  in  lines  standing  in  two,'  three,  or  four  rows  back  from  the 
face,  the  waste  being  piled  behind  as  the  work  advances.  In  this 
manner,  by  exercising  care,  many  sticks  of  timber  can  be  recovered 
before  the  weight  settles  so  heavily  on  the  refuse  rock  as  to  render 
it  impossible  to  remove  them.  Some  flat  veins  make  little  or  no 
waste.  It  is  then  necessary  to  follow  the  "  pillar  and  stall "  system 
of  extraction,  considerable  blocks  being  left  to  sustain  the  roof. 
Posts  and  caps  are  used  in  this  system  also.  Frequently  the  cap.« 
reach  in  a  continuous  line  from  post  to  post,  joining  the  next  set, 
the  ends  of  two  caps  resting  on  a  single  post,  the  combined  sets 
being  a  hundred  feet  or  more  in  width.  Large  timbers  thus 
placed  will  support  great  weight,  but  if  small  rocks  fall  from  the 
roof,  lagging  also  must  be  employed.  This  is  the  system  much  in 
use  in  California  drift-gravel  mines. 

When  a  vein  lying  nearly  or  quite  horizontal,  and  making  no 
waste,  is  to  be  mined,  a  drift  should  be  run  along  the  lowest  por- 
tion of  the  deposit,  this  point  having  been  reached  by  incline 
or  shaft.  The  work  advances  towards  the  surface,  good-sized 
pillars  being  left  to  sustain  the  roof.  If  timber  be  necessary,  it 
is  put  in  place  in  the  manner  required.  The  work  having  ad- 
vanced sufficiently  toward  the  surface,  the  pillars  may  now  be  cut 
out  at  the  back  end,  while  the  work  progresses  as  before.  As 
the  pillars  are  removed  more  timber  must  be  put  in,  or  waste  from 
the  surface  must  be  piled  in  cribs  of  timber  built  in  the  workings 
already  made.  Usually  some  timber  can  be  recovered  in  this 
way,  and  the  caving  of  the  roof,  after  the  complete  removal  of 
the  ore  or  mineral,  does  no  harm.  The  main  gangway  should 
be  substantially  timbered,  if  necessary,  as  it  is  desirable  to  keep 
it  open  to  the  lowest  working  level  at  all  times. 


160  TIMBERING   AND  MINING 

The  "long  wall"  system  of  extracting  ore  is  usually  carried 
from  the  surface  inward,  a  main  gangway  having  been  first  driven 
ahead  to  a  connection  with  a  ventilating  shaft,  when  possible. 
All  the  ore  is  removed  at  once,  the  waste  being  thrown  back  of 
the  miners,  who  carry  the  breast  forward  with  the  center  consider- 
ably in  advance  of  the  sides,  the  excavation  being  in  form  some- 
what like  the  letter  A,  with  the  apex  forward.  The  waste  is 
thrown  into  the  center  to  support  the  roof,  while  the  side  passages 
permit  of  a  free  circulation  of  air  all  along  the  face. 

Veins  of  10  ft.  or  more  in  thickness,  which  lie  at  an  angle 
lower  than  35°  may  be  worked  economically  by  sinking  an  in- 
clined shaft  in  the  foot-wall,  25  ft.  beneath  the  vein,  driving 
levels  to  and  across  the  vein,  cutting  ore  pockets  at  each  level  in 
the  country  rock  between  the  shaft  and  the  vein,  and  stoping 
the  ore  body  in  blocks.  Filling  may  be  obtained  from  chambers 
cut  in  the  hanging-wall  country,  or  it  may  be  broken  in  an  open 
cut  on  the  surface  and  sent  down  into  the  mine  in  cars,  an  in- 
clined shaft  having  been  sunk  in  the  hanging-wall  for  this  purpose, 
from  which  drifts  extend  over  the  stopes.  In  lieu  of  this  latter 
arrangement,  the  waste  rock  may  be  sent  down  in  cars  in  the 
working  shaft  sunk  in  the  foot-wall,  and  these  run  off  at  the  level 
above  that  to  be  filled,  and  the  filling  run  down  into  the  stope 
below  through  mill  holes  provided  for  the  purpose. 


CHAPTER  XVII 

RAISES   FOR  CONNECTION   OF   LEVELS 

THE  driving  of  raises  in  all  mines  is  important,  and  in  many 
of  them  necessarily  precedes  the  commencement  of  stoping. 
Ordinarily,  raises  are  cut  either  by  machine  or  handwork  without 
any  more  timber  than  absolutely  necessary  to  enable  the  miners 
to  climb  up  to  the  top  and  renew  drilling  after  a  blast.  Stout 
stulls  are  placed  in  hitches  as  the  work  proceeds  upward,  and  the 
men  stand  while  drilling  on  platforms  laid  on  the  uppermost 
stulls.  When  ready  to  blast,  the  platform  is  piled  up  to  one  side, 
and  the  rock  broken  by  the  shots  falls  down  the  raise,  to  be  drawn 
out  at  the  bottom,  where  a  chute  is  usually  built,  though  in  many 
cases  the  rock  falls  to  the  floor  of  the  level  below  and  is  shoveled 
into  cars  and  trammed  away.  There  are  instances,  however, 
where  it  is  desirable  to  divide  the  raise  into  two  compartments,  for 
the  purpose  of  making  it  a  permanent  ore  pass  and  also  to  afford  a 
means  of  ventilation.  In  this  case  a  line  of  stulls  is  set  up  at  or 
near  the  middle  of  the  raise,  at  right  angles  to  the  angle  of  the 
raise  itself,  and  on  the  ore-pass  side  is  spiked  2-in.  planks.  In 
the  opposite  compartment  is  placed  a  ladder  to  facilitate  the  pas- 
sage of  men  from  level  to  level.  It  will  be  understood  that  a 
raise  of  the  character  here  described  is  entirely  different  from  the 
mill  holes  carried  up  in  a  stope. 

Sometimes  it  is  desirable  to  timber  a  raise  —  in  fact,  to  so 
construct  it  that  it  may,  when  finished,  be  used  as  a  working 
shaft,  or  it  may  be  desirable  to  connect  it  with  a  shaft  sunk  from 
the  surface,  or  from  some  level  above.  Rapid  shaft  building,  as 
it  may  be  called,  is  often  accomplished  by  driving  a  number  of 
raises  simultaneously  from  several  levels,  the  series  being  finally 
connected,  making  one  continuous  shaft.  It  is  scarcely  necessary 
to  say  that  the  greatest  care  on  the  part  of  the  mine  surveyor 
is  necessary  when  such  work  is  undertaken,  as  hoisting  shafts 
require  absolutely  straight  alinement,  and  no  off-sets  are  permis- 

161 


162  TIMBERING  AND   MINING 

sible.  A  competent  mine  surveyor  can  lay  out  the  work  with  such 
accuracy  that  the  several  sections  of  the  series  of  raises  will  meet 
within  a  small  fraction  of  an  inch.  It  is,  however,  wise  to  make 
raises  of  such  liberal  size  that  any  small  discrepancy  in  alinement 
may  be  corrected  by  changing  the  thickness  of  the  guides  a  little. 
Contemplating  a  series  of  vertical  raises  driven  to  connect  with 
an  existing  shaft,  each  section  will  be  a  counterpart  of  the  others. 
.At  the  places  selected  for  beginning  the  raise,  cut  out  a  station 
large  enough  to  accommodate  the  loading  chute  and  car  tracks, 
either  single  or  double,  as  required:  for  a  single  track  of  ordinary 
gage  — say  18  in.  —  cut  this  station  12  ft.  high  and  as  wide  and 
long  as  the  shaft  requires.  Give  sufficient  working  room  on  three 
sides  of  the  car,  at  least,  and  space  for  the  chute  timbers  on  the 
fourth  side.  If  the  drift  has  been  cut  of  liberal  size,  it  is  quite 
likely  to  afford  room  for  all  this  without  cutting  out  additional 
ground  at  the  time.  This  station  should  be  at  one  side  of  the 
shaft,  not  immediately  below  it. 

When  the  raise  has  been  started  at  one  side  of  the  drift, 
hitches  should  be  cut  at  each  end  of  the  raise  (or  shaft,  as  we  may 
call  it,  in  anticipation  of  its  purpose)  to  hold  long,  heavy  timbers 
which  are  to  serve  as  bearers,  the  same  as  in  sinking  a  shaft. 
The  size  of  the  timbers  may  be  of  the  same  dimensions  as  those 
in  the  shaft  sunk  above,  or  may  vary,  in  the  discretion  of  the 
superintendent,  with  the  character  of  the  ground,  it  being  per- 
missible to  employ  smaller  timbers  in  ground  that  is  hard  and 
firm  than  in  ground  that  is  soft  and  likely  to  cave.  The  bearers 
are  to  support  the  shaft  timbers  and  also  form  a  substantial  back 
for  the  top  of  the  rock  bin  and  loading  chute.  Up  to  the  time 
the  raise  has  advanced  10  ft.  all  of  the  rock  broken  should  be 
shoveled  into  cars  from  the  floors  and  trammed  away.  Then 
the  bearers  should  be  put  in  place  and  firmly  wedged.  They 
must  not  only  be  level,  but  should  conform  exactly  to  the  inside 
dimensions  of  the  shaft  or  raise. 

When  the  raise  is  up  10  ft.  above  the  back  of  the  station  and 
the  bearers  are  in  place,  the  first  set  of  shaft  timbers  should  be 
placed  in  position.  These  consist  of  two  wall  plates  and  two 
end  plates.  The  style  of  framing  is  left  to  the  miner.  Either  the 
overlap  or  the  dovetail  corner  is  good.  The  latter  is  particularly 
applicable  to  inclined  shafts,  but  may  be  used  also  in  vertical 
shafts.  When  the  lowest  set  of  plates  has  been  fixed  in  position 


RAISES  FOR  CONNECTION  OF   LEVELS  163 

and  securely  wedged  to  exact  place,  set  up  the  posts  on  each 
corner,  being  careful  that  they  rest  squarely  in  the  daps  provided 
for  them  on  the  plates.  On  these  four  posts  place  the  second  set 
of  wall  plates;  block  and  wedge  them  firmly,  as  before;  put  lag- 
ging in  position  all  round,  if  necessary,  and  block  it  with  rocks 
or  wedges.  The  first  shaft  set  is  then  complete.  Build  the 
(temporary)  rock  bin  beneath  one  compartment  Place  a  ladder 
on  the  floor  of  the  station  leading  up  to  the  first  set. 

This  ladder  may  be  placed  in  any  desired  position,  clear  of 
the  track,  to  reach  the  first  set.  Two  movable  ladders  must  now 
be  provided,  to  be  used  as  the  work  progresses,  one  about  6  ft. 
6  in.  long,  the  other  about  12  ft.  Also  make  a  number  of  perma- 
nent ladders  about  16  ft.  6  in.  long,  to  reach  the  height  of  three 
sets,  when  resting  at  an  inclination  of  about  70°.  In  a  vertical 
shaft,  strong  ladders,  securely  placed,  are  absolutely  necessary. 
Never  place  ladders  vertically  when  they  can  be  set  at  an  inclina- 
tion. Put  them  in  the  man  way  compartment,  on  the  side  next 
to  the  dividers.  This  leaves  the  other  end  of  the  same  compart- 
ment open  for  pipes,  and  for  the  passing  of  timbers,  machines 
and  supplies  from  place  to  place  while  the  raise  is  being  driven. 
At  every  third  set,  above  the  first,  spike  a  2  X  12-in.  plank 
across  the  manway  compartment,  parallel  with  the  dividers,  and 
22  in.  from  it.  On  the  divider  spike  a  piece  of  2-in.  lagging  and 
on  these  spike  two  pieces  of  2  X  12-in.  plank  side  by  side,  parallel 
with  the  wall  plates  and  at  one  side  of  the  shaft.  This  leaves  a 
manhole  at  every  third  set.  The  ladders  should  be  placed  with 
the  foot  resting  on  the  platform  8  in.  from  the  wall  plate,  and 
should  extend  at  least  12  in.  above  the  set  at  the  upper  end.  It 
is  also  a  good  idea  to  provide  a  substantial,  safe  hand-hold  a  foot 
above  the  top  of  each  ladder,  as  an  aid  to  men  who  may  be  carry- 
ing tools,  etc.,  up  the  raise.  An  iron  dog  8  in.  wide  driven  firmly 
into  the  lagging  at  the  side  of  the  shaft  or  a  piece  of  1  X  4  spiked 
to  the  posts,  will  be  sufficient.  The  ladders  should  be  placed 
directly  above  each  other,  inclining  always  in  the  same  direction, 
so  that  when  a  man  reaches  the  top  of  a  ladder  he  steps  to  one 
side  onto  the  plank  platform  and  back  to  the  foot  of  the  next 
ladder,  to  continue  his  upward  climb. 

To  hoist  timber  quickly  and  safely  while  the  work  of  raising 
is  in  progress,  a  portion  of  the  open  space  in  the  manway  should 
be  boxed  in  on  four  sides,  providing  a  chute  through  which  timber 


164  TIMBERING  AND  MINING 

and  other  things  may  be  hoisted  with  a  block  and  tackle,  or  by 
other  means.  If  this  chute  be  made  tight  it  will  greatly  aid 
ventilation  —  a  most  important  matter,  when  raising,  under  any 
conditions. 

Having  described  the  method  of  placing  ladders,  platforms, 
etc.,  we  may  now  return  to  mining  operations.  Assuming  the 
raise  now  to  have  been  cut  to  a  height  of  10  ft.  above  the  bearers, 
and  one  complete  set  to  be  in  position,  place  a  short  ladder  from 
the  first  platform  to  the  top  of  the  set  just  put  in.  Over  the 
manway  compartment  construct  a  heavy  bulkhead  of  8  X  8-in. 
timbers,  leaving  the  rock  compartment  open.  Spike  lagging 
vertically  on  the  four  sides  of  the  rock  compartment.  Two 
of  the  timbers  of  the  bulkhead  may  be  left  out  until  ready  to  go 
below.  A  full  round  of  holes  of  moderate  depth  should  be  drilled 
by  hand  or  by  machine.  When  ready  to  blast,  if  a  machine  has 
been  used,  lower  it  through  the  hole  in  the  bulkhead  and  place 
it  and  other  tools  on  a  temporary  platform  on  the  set  below. 
The  miners  spit  the  fuses  on  that  side  of  the  raise  over  the  bulk- 
head, the  holes  having  been  pointed  so  as  to  throw  the  rock  on 
that  side  as  much  as  possible.  After  spitting  the  fuses,  the  men 
go  down  through  the  hole  in  the  bulkhead,  pulling  the  loose 
timbers  in  place  and  descending  to  the  level  below.  When  all 
the  lighted  holes  have  gone  off  and  the  smoke  has  had  time  to 
clear,  the  men  return  to  the  top  of  the  raise  and  knock  off  two  or 
three  lagging  of  the  rock  compartment,  so  that  they  may  climb 
into  it  and  upon  the  bulkhead  and  its  load  of  rock.  The  lagging 
is  again  spiked  fast  and  the  loose  rock  overhead  barred  down.  All 
large  pieces  are  broken  to  a  size  small  enough  to  pass  the  chute 
door  below  and  the  rock  is  shoveled  into  the  rock  compartment, 
clearing  the  bulkhead.  When  the  back  has  been  cleared  up,  the 
remainder  of  the  holes  of  the  round  are  fired  the  men  going  below 
through  an  opening  in  the  bulkhead  as  before,  closing  the  hole  after 
them.  If  the  broken  rock  has  filled  up  the  rock  compartment, 
a  portion  of  it  may  be  drawn  off  into  cars  and  trammed  away 
until  the  rock  compartment  has  been  relieved  sufficiently  to  permit 
the  miners  to  return  to  work  through  a  hole  made  by  knocking 
off  the  lagging,  as  before.  Again  the  loose  rock  is  barred  down 
and  the  bulkhead  cleared,  and  then  the  back  is  ready  for  another 
full  round.  When  the  rock  bin  has  once  been  filled  it  is  not 
necessary  to  exercise  so  much  care  in  the  pointing  and  loading  of 


RAISES  FOR  CONNECTION  OF   LEVELS  165 

holes,  as  the  danger  of  knocking  out  the  chute  timbers  and  the  door 
is  then  practically  at  an  end. 

When  sufficient  headway  has  been  made  another  set  is  placed 
in  position  and  the  bulkhead  is  moved  up  a  set.  The  broken 
rock  is  never  drawn  off  after  blasting  lower  than  the  bottom  of 
the  last  set  placed,  and  the  rock  shoveled  from  the  bulkhead  and 
barred  down  from  the  back  usually  fills  the  rock  compartment 
so  nearly  full  as  to  afford  ample  protection  to  the  timbers  not 
protected  by  bulkhead.  In  this  manner  the  work  proceeds. 
After  each  round  of  holes  is  drilled  the  miners  place  their  tools 
on  a  temporary  platform  built  on  the  first  set  below  the  bulkhead, 
spit  the  fuses,  and  retire  through  a  hole  in  the  bulkhead,  closing 
the  hole  after  them.  Returning,  they  break  a  way  through  the 
lagging  into  the  rock  compartment,  drawing  off  as  much  rock  as 
necessary  to  do  so,  and  after  clearing  up  proceed  with  the  drilling 
of  another  round.  When  the  work  is  well  advanced,  the  long, 
permanent  ladders  may  be  put  in  place. 

The  question  of  ventilation  is  all-important,  but  may  usually 
be  solved  by  carrying  up  a  pipe  close  to  the  bulkhead,  or  the  timber 
chute  built  in  the  manway  may  be  used  for  this  purpose.  About 
the  only  ground  in  which  this  method  of  driving  a  raise  will  not 
prove  satisfactory  is  wet,  clayey  ground  which  would  pack  in 
the  chute.  In  such  cases  it  would  probably  be  better  to  place  a 
bulkhead  over  the  rock  compartment  also,  leaving  open  spaces 
of  6  to  10  inches  between  the  timbers.  This  would  act  as  a  grizzly 
and  retard  to  some  extent  the  force  of  the  flying  rock  when  blast- 
ing. In  such  ground,  however,  it  is  generally  better  to  raise  with 
stulls,  placing  the  permanent  shaft  timbers  when  the  job  has  been 
completed. 


CHAPTER  XVIII 

STOPING  AND  FILLING  IN  A  MINE  HAVING  WEAK 

WALLS 

IN  a  former  chapter  was  given  a  description  of  stoping  in  a 
vein  of  moderate  width,  first,  in  a  clean  vein,  breaking  all  of  the 
ore  and  drawing  out  only  sufficient  to  allow  the  necessary  head 
room  for  miners  drilling  in  the  backs.  By  this  method  the  ore 
is  drawn  off  into  cars  on  the  track  in  the  level  beneath.  Second, 
mining  in  a'  vein  in  which  considerable  waste  occurs,  or  where 
the  walls  are  loose  and  shelly,  coming  down  with  the  ore  and  un- 
avoidably mixing  with  it.  When  this  condition  obtains,  or  the 
vein  is  so  small  that  a  portion  of  one  or  both  walls  must  be  broken 
to  allow  working  room,  mill  holes  are  carried  up  in  the  stope,  the 
ore  is  shoveled  into  these  while  the  waste  accumulates  in  the  stope, 
keeping  the  men  up  to  the  back,  or  if  there  is  too  little  waste 
for  this,  a  means  of  providing  it  was  suggested.  In  mining  many 
conditions  are  found  in  veins,  and  the  methods  of  meeting  these 
conditions  vary  almost  as  much  as  the  variety  of  conditions 
themselves. 

Following  is  a  description  of  mining  a  vein  of  iron  ore  at 
Soudan,  Minnesota,  written  by  D.  H.  Bacon,  in  the  "Transactions 
of  the  American  Institute  of  Mining  Engineers,"  Vol.  XXI, 
page  299.  The  method  there  described  is  somewhat  different  in 
some  respects  from  those  previously  mentioned.  It  is  thoroughly 
practical  and  readily  applied  where  the  conditions  are  in  any 
manner  similar. 

"The  iron  ore  deposits  worked  by  the  Minnesota  Iron  Com- 
pany, at  Soudan,  Minnesota,  occur  in  lenses  200  to  1000  ft.  long 
and  5  to  80  ft.  wide,  and  stand  at  an  angle  of  65  to  75  degrees, 
with  a  vertical  height  of  250  to  500  ft.,  other  lenses  occurring 
below.  A  number  of  the  deposits  were  first  worked  as  open  pits, 
which  in  some  cases  were  carried  to  a  depth  of  150  ft.,  when, 
owing  to  the  weakness  of  the  walls,  underground  mining  was 

166 


MINE   HAVING  WEAK   WALLS  167 

adopted.  While  the  ore  was  being  removed  from  the  open  pit, 
shafts  were  in  several  instances  sunk  into  the  foot-wall,  the  in- 
tention being  to  mine  the  ore  with  breast-stopes  of  an  approxi- 
mate height  of  20  ft.,  followed  by  underhand  stopes  of  the  same 
height,  leaving  floors  between  of  the  necessary  thickness  to  sup- 
port the  walls,  or  to  effect  the  removal  of  the  ore  by  means  of 
what  is  known  as  the  "stall  system."  As  work  progressed,  how- 
ever, it  was  found  that  the  walls  (which  are  chlorite)  were  too 
weak  to  permit  the  working  of  breast-stopes  20  ft.  high,  there 
being  frequent  heavy  falls  of  ground  from  the  hanging-wall,  and 
sometimes  from  the  foot.  The  plan  of  following  breast-stopes 
with  underhand  stopes  was,  therefore,  abandoned.  By  working 
breast-stopes  only,  but  little  more  than  one-half  of  the  ore  could 
be  removed,  and  that  only  at  an  excessive  cost,  the  ore  being  so 
hard  that  power-drills  with  3^-in.  pistons,  and  6-in.  stroke,  work- 
ing under  60  Ib.  of  compressed  air,  are  able  to  drill  but  6  ft.  in 
10  hours  as  a  yearly  average,  while  from  6  in.  to  2  ft.  is  a  common 
result  of  10  hours'  drilling.  It  was  plain  that  some  other  system 
of  mining  must  be  adopted,  and  it  was  proposed  to  sink  by  levels 
of  75  ft.,  carrying  in  the  cross-cuts  from  the  shafts  and  working 
out  the  ore  each  way  from  the  shaft  from  foot  to  hanging,  and 
from  15  to  20  ft.  in  height.  When  this  has  been  done,  drift  sets 
consisting  of  caps  and  legs  are  set  up  the  whole  length  of  the  open- 
ing and  connected  with  the  cross-cut;  the  necessary  openings  for 
ladder  ways  and  chutes  or  mills  are  timbered  from  the  floor  to  a 
few  feet  above  the  top  of  the  drift  sets;  loose  rock  is  run  in,  and 
the  opening  is  filled  to  such  a  height  that  from  2  to  5  ft.  of  loose 
rock  will  be  over  the  timber.  About  10  ft.  of  the  roof  (or  back) 
is  then  blasted  down,  broken  up,  and  shoveled  into  the  chutes, 
from  which  it  is  let  into  the  tram-cars  standing  in  the  drift. 

"  As  the  stope  is  extended  filling  follows,  rock  being  let  in  and 
the  chutes  and  ladder  ways  cribbed  up  as  before.  It  has  been  the 
practice  to  construct  these  chutes  and  ladder  ways  (which  measure 
5  X  5  ft.  inside)  of  round  timber,  flattened  at  the  ends,  to  line 
the  sides  of  the  chutes  with  plank,  placed  vertically,  and  to  cover 
the  bottom  with  short  pieces  of  rails.  Each  chute  is  also  provided 
with  an  iron  spout,  so  adjusted  that  it  may  be  raised  or  lowered, 
for  running  ore  into  cars.  It  was  thought  that  these  chutes 
would  wear  out  before  the  ore  in  the  roof  was  exhausted,  but, 
should  this  occur,  a  ladder  way  could  be  converted  into  a  chute. 


168 


TIMBERING  AND  MINING 


"The  rock  for  filling  is  obtained  by  putting  raises, either  in  the 
foot  or  hanging,  close  to  the  ore,  from  the  first  level  to  the  open 
pit,  from  the  second  level  to  the  first,  and  so  on.  The  raises  are 
cribbed  through  the  different  levels,  and  when  rock  is  wanted  at 
one  of  the  upper  levels  it  is  obtained  by  filling  the  raise  below  that 
point  with  rock  or  by  inserting  timber  to  prevent  the  rock  de- 
scending below  the  place  at  which  it  is  needed,  and  where  it  is 
run  into  tram-cars.  Two  years'  trial  of  this  system  proved  it  to 


.-••&%&$?. 

•p^s-^'iX-W^- 


4th  Level 


Level 


h  Level 


FIG.  72 


be  satisfactory.  In  the  winter,  when  the  superincumbent  rock 
is  frozen,  it  has  been  found  possible  to  remove  nearly  all  of  the 
ore  in  the  upper  levels,  and,  after  the  first  level  is  exhausted,  rock 
is  taken  from  it  for  those  below.  Rock  to  fill  the  first  level,  and 
also  any  other  levels  that  may  need  filling  before  the  first  level 
is  exhausted,  is  largely  supplied  from  the  accumulation  from  the 
loose  sides  of  the  pit,  and  when  that  is  not  sufficient,  the  walls  of 
the  open  pit  are  blasted  in.  In  narrow  veins  the  needed  filling 
is  sometimes  obtained  by  breaking  down  the  walls  underground, 


MINE   HAVING  WEAK  WALLS 


169 


and  in  other  cases  piles  of  waste  rock  on  the  surface  have  been 
utilized.     One  advantage  of  this  method  is,  that  the  rock  broken 


FIG.  73.  —  Vertical  Cross-section,  showing  the  Raise  on  the  Foot-wall 

from  the  walls  in  blasting,  or  that  coming  from  seams  in  the  ore, 
is  left  almost  where  it  falls,  causing  no  expense  for  tramming  or 
hoisting  and  often  none  for  throwing  to  one  side. 


170 


TIMBERING   AND   MINING 


"  Experience  has  shown  back-stoping  to  be  cheaper  than  under- 
hand. The  roof  is  always  near  and  easily  examined,  and  as  the 
mills  are  seldom  over  50  ft.  apart,  the  trammers  can  work  at  a 
pile  of  ore  from  either  side  and  not  delay  the  drillers,  nor  stand 
under  ground  that  has  not  yet  been  made  safe.  When  the  ore 
body  is  very  wide  it  has  occasionally  been  necessary  to  leave  small 
pillars  near  the  hanging,  but  the  loss  of  ore  has  been  slight.  Slabs 
in  the  back  are  often  temporarily  supported  by  cribs  of  chute- 
timber,  built  on  the  filling  and  wedged  tightly.  Holes  are  then 
bored  over  the  slabs,  the  cribs  are  removed  and  the  dangerous 


FIG.  74.  —  Showing  Arrangement  of  Chutes 

rock  broken  down.     The  timber  is  then  used  to  support  other 
slabs,  or  to  extend  the  chutes  and  ladder  ways.* 

"In  each  shaft  is  the  usual  ladder  way;  but  as  a  sure  means 
of  escape  in  the  event  of  fire  in  the  shaft,  raises  are  put  through 
from  each  level  to  the  next  above,  about  midway  between  the 
ore  body  and  the  shaft,  in  which  are  ladders  which  can  be  used 


*The  small  pneumatic  hammer  drills  now  in  use  in  many  mines  are  most 
excellent  devices  for  block-holing  dangerous  slabs  hanging  in  the  stope,  as 
they  will  drill  a  hole  quickly  and  with  a  minimum  jarring  of  the  threatening 
rock,  which  the  heavy  strokes  of  a  large  machine-drill  may  cause  to  fall  when 
not  wanted. 


MINE   HAVING   WEAK   WALLS  171 

should  the  necessity  arise.  It  has  not  been  found  necessary  to 
select  particularly  large  timbers  for  drift  sets  or  to  place  them  very 
close  together,  80  ft.  of  broken  rock  on  some  of  the  sets  having 
broken  none  of  the  timber." 

The  accompanying  illustrations  will  make  this  system  of 
mining  plain.  Fig.  72  is  a  longitudinal  section,  showing  the 
progress  of  the  work  on  three  levels.  Fig.  73  is  a  vertical  cross- 
section,  showing  the  raise  on  the  foot-wall.  Fig.  74  is  a  section 
showing  the  arrangement  and  construction  of  the  chutes. 


CHAPTER  XIX 

THE  CAVING  SYSTEM    PRACTISED   AT  THE    PEWABIC 
MINE,   IRON   MOUNTAIN,   MICHIGAN 

IN  some  of  the  iron  mines  of  Michigan  and  Minnesota,  what  is 
known  as  the  caving  system  of  mining  is  in  vogue.  This  method 
of  removing  ore  with  the  use  of  little  or  no  timber  has  been  de- 
scribed by  E.  F.  Brown  in  the  proceedings  of  the  Lake  Superior 
Mining  Institute. 

"  The  system  of  mining  herein  described  has  been  in  successful 
operation  at  the  Pewabic  Mine,  Iron  Mountain,  Michigan,  for  a 
period  of  three  years,  and  about  six  hundred  thousand  tons  of 
iron  ore  have  been  extracted  from  the  points  in  the  mine  where  it 
has  been  found  advantageous  to  make  use  of  this  method  exclu- 
sively. This  system  has  been  employed  most  extensively  upon 
a  large  body  of  highly  silicious,  hard  hematite  ore,  of  uniform 
quality.  For  convenience  in  operating,  the  ore  body  is  first 
divided  into  blocks,  having  a  length,  on  the  trend  of  the  strata,  of 
about  250  ft.,  the  width  of  the  blocks  depending  upon  the  distance 
between  the  slate  walls,  or  foot  and  hanging.  The  height  is  the 
distance  between  levels,  ordinarily  100  ft.  The  accompanying 
sketches  show  one  of  these  blocks  of  ore  in  various  stages  of 
preparation  for  mining,  also  the  condition  of  the  over-burden, 
consisting  of  broken  sandstone  and  old  timber,  which  had  been 
caved  by  earlier  mining  operations. 

"The  plan  of  cross-cutting  and  raising  in  blocking  out  the 
ore  is  shown  in  Fig.  75;  also  the  location  of  the  ore  with  reference 
to  the  main  level.  The  main  level  is  driven  in  the  hanging-wall 
slate,  about  20  ft.  from  the  ore  body,  and  parallel  with  its  trend. 
From  the  main  level,  cross-cuts  are  extended  across  the  ore  body 
to  the  foot-wall.  We  usually  make  four  cross-cuts,  thus  dividing 
a  block  of  ground  250  ft.  long  into  three  blocks  of  about  80  ft. 
each.  Adjacent  to  the  two  cross-cuts,  which  mark  the  eastern 
and  western  boundaries  of  the  original  block,  we  start  raises 

172 


S  i  I  i  c  i  o;u  b  _; S  l:a  t  e -s 


H  a  log  i  n  g 


FIG.    75.  —  Showing   Drifts,  Cross-cuts  and  Raises   Preparatory  to  "  Block 
Caving,"  Pewabic  Mine 


Surface 


Sandstone       Capping 


Broken'Sandstone     and       Timber 


FIG.  76.  —  Cross-section,  "  Block  Caving, "  Pewabic  Mine 


174  TIMBERING   AND  MINING 

50  ft.  distant  from  each  other,  and  extend  these  raises  80  ft., 
or  within  20  ft.  of  the  level  immediately  above. 

"  Figs.  76  and  77  represent  vertical  sections  taken  through 
A-B  and  C-D  of  Fig.  75,  and  show  the  raises  in  detail.  Chutes 
are  constructed  at  the  bottom  of  the  raises,  and,  commencing  at 
the  top,  underhand  stoping  is  carried  on  until  a  trench  8  ft.  wide 
and  80  ft.  deep  has  been  cut  across  the  ore  body  from  foot  to 
hanging  wall. 

"In  underhand  stoping  the  ore  falls  into  the  chutes  when 
blasted,  and  is  run  into  the  tram  cars  by  gravity.  During  the 
time  required  to  cut  the  trenches  across  the  ends  of  the  block, 
we  are  also  employed  in  undercutting  it,  and  when  the  trenches 
are  completed  we  have  the  bottom  of  the  block  about  in  the  con- 
dition shown  by  Fig.  78.  That  is,  we  have  two  strong  pillars 
alongside  of  the  main  cross-cuts  on  the  ends  of  the  block,  while 
the  balance  of  the  ground  is  resting  on  small  legs  of  ore,  irregular 
in  size  and  shape.  These  legs  and  pillars  are  then  made  as  small 
as  is  consistent  with  safety  to  the  miners.  The  remaining  portion 
is  then  drilled,  and  when  all  have  been  drilled  they  are  blasted 
in  sections.  The  ends  of  the  block  being  cut  off  and  the  entire 
block  thoroughly  undercut,  the  ore  soon  begins  to  cave.  This 
usually  occurs  in  large  masses  of  many  hundreds  of  tons  each. 

"To  illustrate  the  hardness  of  the  ground  and  the  results 
obtained,  it  may  be  well  to  state  that  no  timber  is  used  in  prose- 
cuting the  work  just  outlined,  and  that  it  requires  several  weeks 
for  a  block  of  this  ore  to  settle  a  distance  of  7  ft.,  but  within  six 
or  eight  months  the  ore  becomes  crushed  so  that  four-fifths  of  the 
entire  block  could  be  put  through  a  3-in.  opening.  After  the 
block  of  ore  has  settled  down  to  the  original  level,  and  been 
sufficiently  crushed  to  allow  easy  driving  of  cross-cuts,  the  two 
cross-cuts  in  the  central  portion  of  the  block,  as  shown  in  Fig.  79, 
are  advanced  through  the  caved  ore,  and  from  these  cross-cuts 
drifts  are  run  to  the  eastern  and  western  boundaries  of  the  caved 
territory.  These  drifts  are  usually  located  about  25  ft.  apart,  on 
the  line  of  the  cross-cut.  The  drift  nearest  the  foot-wall  is  con- 
nected with  the  adjacent  cross-cut,  and  from  this  drift  short 
cross-cuts  are  extended,  at  intervals,  to  the  foot-wall. 

"These  drifts  and  cross-cuts  are  all  closely  timbered,  and 
after  the  initial  timbering  require  but  little  attention  in  the  way 
of  repairs.  The  work  of  mining  is  now  commenced  by  allowing 


THE  CAVING  SYSTEM 


175 


the  caved  ore  to  run  into  the  drifts  and  cross-cuts  through  the 
opening  in  the  end,  or  breast,  of  each.  The  broken  ore  is  simply 
shoveled  into  the  tram-cars  and  taken  to  the  shafts,  the  breast 
of  the  drifts  always  being  full  of  broken  ore.  When  a  full  output 
is  desired,  the  crew  consists  of  one  miner  and  four  shovelers  at 
each  of  the  points  in  operation.  Two  of  the  shovelers  are  always 
employed  in  filling  the  cars,  while  the  other  two  are  tramming 
to  the  main  level.  No  drilling  is  required  and  but  little  powder 
is  used  in  blasting. 


Surface 


FIG.  77.  —  Longitudinal  Section,  "Block  Caving,"  Pewabic  Mine 

"Drawing  the  ore  in  this  manner  forms  funnel-shaped  spaces 
in  the  body  of  broken  ore,  and  these  are  eventually  filled  by  the 
caving  of  the  timber  and  broken  sandstone  from  the  old  level 
above.  When  the  ore  has  been  so  far  removed,  at  any  point, 
that  the  waste  material  shows  in  the  working  faces,  we  blast  a 
few  of  the  timbers  in  the  drift  and  draw  our  point  of  operations 
nearer  to  one  of  the  main  cross-cuts.  This  operation  is  continued, 
and  repeated  until  the  ore  in  the  territory  formerly  traversed  by 
the  drifts  has  been  exhausted  and  replaced  by  the  waste  from 
above.  Other  drifts  from  the  main  cross-cuts  are  then  driven  in 


176 


TIMBERING  AND   MINING 


Do  OQ  o 

o  o 


o 


n 


DH  n 

U  U    U 


FIG.  78.  —  Showing  Block  of  Ground  ready  for  Caving,  Pewabic  Mine 


FIG.  79.  —  Showing  Drifts  and  Cross-cuts  through  the  Block  after  being 
Caved,  Pewabic  Mine 


THE  CAVING  SYSTEM  177 

the  pillars  remaining  between  the  first  drifts,  and  the  operation 
repeated  as  in  the  first  work.  In  actual  work,  it  is  found  possible 
to  draw  the  ore  for  three  or  four  feet  on  either  side  of  these  drifts : 
consequently  the  second  set  of  drifts  practically  cleans  up  the 
broken  ore. 

"The  typical  block  of  ore  herein  described  contained,  origi- 
nally, about  350,000  tons  of  ore,  and  it  has  yielded  about  120,000 
tons  during  the  first  shipping  season.  A  much  larger  output 
could  have  been  attained  if  desired.  We  have  never  had  any 
fatal  accidents  in  connection  with  operating  under  this  system, 
and  it  can,  without  exaggeration,  be  called  a  safe  method  of 
mining.  With  modifications  to  accommodate  varying  conditions, 
this  system  has  been  applied  to  the  mining  of  soft  ore  bodies,  and 
the  results  obtained  in  this  direction  have  been  satisfactory." 


CHAPTER  XX 

STOPING   IN   SWELLING   GROUND 

IN  sloping  in  veins  where  filling  is  necessary,  it  is  not  always 
expedient  or  possible,  without  great  expense,  to  obtain  the  neces- 
sary filling  from  or  near  the  surface.  In  some  of  the  mines  of 
California,  where  the  veins  are  wide  (as  the  Utica,  at  Angels,  in 
Calaveras  County),  or  of  moderate  width  (as  at  the  Gwin  mine), 
the  necessary  filling  is  secured  by  excavating  chambers  in  the 
country  rock  of  the  walls  —  usually  on  the  hanging  side.  This 
method  has  been  found  to  meet  the  usual  requirements,  but  it  is 
a  procedure  to  which  considerable  expense  attaches  —  more,  as  a 
rule,  than  in  those  methods  wherein  the  filling  is  obtained  at  the 
surface.  The  mining  methods  in  vogue  in  California,  particularly 
along  the  Mother  Lode,  are  mostly  the  survival  of  the  antiquated 
practice  of  early  days,  many  of  them  most  primitive,  and,  viewed 
from  the  standpoint  of  economy,  have  little  to  recommend  them. 
One  very  noticeable  policy  in  these  mines  is  that  of  demanding 
prompt  returns  from  ore  development  —  a  procedure  often 
accompanied  by  expensive  and  makeshift  methods.  On  the 
other  hand,  the  peculiar  geological  conditions  obtaining  in  many 
of  these  mines  are  such  that  extensive  development  of  ore  bodies 
is  unwise,  owing  to  the  expense  of  keeping  the  workings  on  the 
vein  open  for  considerable  periods. 

In  mines  having  hard-rock  walls,  as  many  levels  as  are  de- 
sired may  be  opened,  and  thousands  of  tons  of  ore  may  be  thus 
advantageously  exposed;  but  where,  as  in  numerous  mines  of 
the  Mother  Lode,  heavy,  swelling  ground  is  common,  it  has  been 
found  to  be  the  part  of  wisdom  not  to  open  too  extensive  workings, 
because  of  the  greatly  increased  expense  of  retimbering  the  levels, 
mill  holes,  chutes,,  and  other  cuttings.  In  these  latter  mines, 
the  usual  practice  is  to  drive  a  cross-cut  or  drift  from  the  station 
to  the  vein.  This  may  or  may  not  at  once  encounter  ore;  if  not, 
a  drift  is  driven  along  the  fissure,  and  this  drift  must  be  timbered 

•  178 


STOPING  IN   SWELLING   GROUND  179 

in  the  most  substantial  manner.  Ordinarily  these  drifts  are  not 
less  than  7  ft.  high,  4  to  5  ft.  wide  at  top,  and  7  to  8  ft.  wide  at 
the  bottom.  These  dimensions  are  all  inside  the  timbers.  Along 
the  fissure  it  makes  little  difference  whether  it  be  filled  with  ore 
or  not:  this  ground  is  generally  heavy.  The  fissures  are  usually 
10  to  40  ft.  between  walls,  and  sometimes  greater  widths  are 
found  —  occasionally  100  ft.  As  soon  as  ore  is  encountered, 
stoping  begins  and  the  ore  is  hoisted  and  sent  to  mill;  drifting 
continues,  and  while  overhand  stopes  are  carried  up  development 
proceeds.  It  may  be  several  hundred  feet  to  the  limit  of  the 
property  or  of  the  ore  shoot  — often  over  1000  ft.,  and  the  main 
workings  in  this  heavy,  swelling,  sometimes  running  ground, 
must  be  kept  open  until  the  entire  level  has  been*  explored,  and 
all  the  ore  between  this  level  and  the  next  above  (generally  100  ft.) 
has  been  extracted  and  hoisted  to  the  surface.  Some  idea  of  the 
character  of  this  ground  and  the  expense  of  working  through  it 
by  this  method  may  be  gained  from  the  statement  that  in  a  cer- 
tain instance  a  drift  of  the  usual  size  was  run  under  contract  a 
distance  of  200  ft.,  and  headway  was  made  at  the  rate  of  5  ft. 
daily,  but  the  work  could  not  be  completed  before  it  became 
necessary  to  return  to  the  portion  first  driven  for  the  purpose  of 
retimbering.  The  timbers  generally  employed  in  working  ground 
of  this  kind  are  from  20  to  30  in.  in  diameter,  but  it  is  by  no  means 
uncommon  to  see  these  big  logs,  split,  crushed,  and  broken  within 
a  few  weeks  of  the  time  they  were  placed  in  position  underground. 

Main  Gangways  Driven  in  the  Country  Rock 

The  advisability  of  cutting  the  main  gangways  in  the  hard 
rock  of  the  walls,  either  foot  or  hanging,  and  developing  and  ex- 
ploiting the  vein  through  a  series  of  cross-cuts,  is  emphasized. 
These  main  gangways,  being  driven  in,  say,  the  foot-wall,  should 
have  cross-cuts  run  at  right  angles  to  the  main  gangway.  These 
cross-cuts  should  be  disposed  at  regular  intervals  for  the  purpose 
of  prospecting  the  fissure  and  rendering  the  ore  discovered  easily 
accessible.  The  distance  of  the  main  gangway  from  the  vein 
must  always  be  determined  by  the  character  of  the  rock  in  which 
it  is  driven,  and  varies  from  20  to  60  ft.  In  all  cases  it  must  be 
sufficient  to  avoid  the  zone  of  rock,  which  will  swell  upon  exposure. 
The  intervals  between  these  cross-cuts  must  be  determined  by 
the  character  of  the  ground  adjacent  to  the  vein  and  by  the  vein 


180  TIMBERING  AND  MINING 

material  itself.  When  the  ground  is  very  bad,  the  cross-cuts 
must  be  closer  than  where  the  ground  is  more  favorable  and  less 
likely  to  crush  the  timbers.  Ordinarily,  if  run  at  intervals  of 
240  ft.,  the  distance  will  be  found  convenient.  Raises  should 
always  be  put  through  to  the  level  above  before  stoping  is  com- 
menced. Too  often  this  important  matter  is  neglected,  owing, 
as  already  stated,  to  the  desire  to  realize  a  profit  on  the  ore  as 
quickly  as  possible  without  indulging  in  anything  that  savors 
(under  the  mistaken  idea  of  economy)  of  unnecessary  expense. 
The  raises  may  be  driven  either  at  the  ends  or  the  middle  of  each 
stope  section.  They  should  be  divided  into  two  compartments, 
and  cut  about  15  ft.  from  each  cross-cut.  This  would  leave  an 
intervening  vein  section  of  210  ft.,  in  which  distance  mill  holes 
could  be  carried  up  at  intervals  of  30  ft.  as  stoping  progresses 
upward.  Generally  speaking,  when  cutting  a  raise  it  is  good 
practice  to  sink  a  winze  immediately  over  it  from  the  level  above, 
to  make  a  connection  with  as  little  delay  as  possible,  in  order 
that  good  ventilation  may  be  secured  and  an  additional  exit 
for  the  miners  provided.  The  increased  efficiency  of  the  work- 
men will  quickly  pay  for  the  added  cost  of  sinking  the  winze. 
The  timber  used  in  the  etope,  if  any  be  required,  may  also  be 
lowered  through  one  compartment  of  the  raise,  which  is  far  better 
than  hoisting  it  and  machines  as  well  from  the  level  below,  though 
the  use  of  small  hoists,  operated  by  independent  electric  motors, 
has  greatly  simplified  the  work  of  taking  machines,  timbers  and 
other  heavy  articles  up  into  stopes. 

This  recalls  a  home-made  device  introduced  into  the  South 
Eureka  mine,  near  Sutter  Creek,  California,  where,  by  an  arrange- 
ment of  three  grooved  sheaves  —  two  at  the  top  of  the  raise  and 
one  at  the  bottom  —  timbers  were  hauled  up  into  the  stope  with 
comparative  ease.  One  of  the  upper  sheaves  was  set  over  one 
compartment  of  the  raise,  the  other  over  the  second  compartment. 
The  third  wheel  was  fixed  at  the  foot  of  the  raise.  The  rope 
passed  up  the  raise  over  the  two  upper  sheaves,  then  downward 
and  under  the  third  sheave  at  the  foot  of  the  raise.  When  it  was 
desired  to  take  timber  into  the  stope,  the  empty  bucket  was  pulled 
by  windlass  up  to  the  upper  part  of  the  raise,  and  the  timber  was 
made  fast,  down  on  the  level,  to  the  rope  in  the  opposite  compart- 
ment. The  bucket  was  then  filled  with  ore,  and  its  weight, 
acting  as  a  counterbalance,  made  the  hoisting  of  the  timber  a 


STOPING  IN  SWELLING  GROUND  181 

matter  of  small  difficulty.  The  scheme  was  rather  dangerous 
in  any  hands  but  those  of  cool  men  who,  with  a  proper  code  of 
signals,  worked  the  device  in  a  satisfactory  manner. 

Returning  to  our  stopes,  when  the  lateral  drift  and  cross-cuts 
have  been  completed,  and  drifts  run  in  the  vein  on  the  level  of 
the  foot-wall  drift,  the  raise  put  through,  chutes  built,  and  all 
preliminary  arrangements  completed,  stoping  may  begin  at  as 
many  places  as  there  are  raises  and  mill  holes  started.  As  soon 
as  connection  has  been  made  from  one  section  of  the  stope  to  the 
next,  ventilation  should  be  as  good  as  it  is  possible  to  make  it, 
this  depending,  of  course,  upon  the  raises  having  been  put  through 
to  the  level  above.  The  ore  should  now  be  removed  rapidly  with 
the  use  of  no  more  timbers  than  necessary.  When  the  ore  has 
been  taken  out,  if  the  excavation  is  not  filled,  the  walls  will  soon 
close  in  and  the  stope  be  lost  forever.  This  generally  should 
result  in  no  particular  harm,  as  the  main  lateral  drift  in  the  foot- 
wall  remains  open.  Where  the  squeezing  of  the  ground,  follow- 
ing the  removal  of  ore,  interferes  with  the  further  progress  of 
stoping,  filling  may  be  obtained  from  the  walls  by  cutting  cham- 
bers, as  shown  in  Fig.  80.  There  will  be  observed  two  chambers, 
one  inclined  upward  from  the  plane  of  the  hanging-wall  side  of 
the  vein;  the  other  running  in  flat.  The  first  is  possible  where 
the  wall  is  firm  and  there  is  little  danger  of  the  rocks  overhead 
falling.  The  second  is  used  where  the  rock  of  the  hanging-wall, 
immediately  adjacent  to  the  vein,  is  loose  and  likely  to  cave.  In 
such  cases  a  cross-cut  is  run  directly  into  the  hanging,  and,  if 
need  be,  the  ground  may  be  timbered  until  firm  rock  is  reached 
beyond,  where  the  chamber  may  be  cut,  either  flat  as  shown,  or 
carried  upward  at  an  angle.  It  is  evident  that  the  lower  chamber 
shown  in  Fig.  80  has  the  advantage,  as  all  rock  broken  therein 
will  pass  out  and  downward  into  the  stope  beneath  by  gravity, 
making  shoveling  unnecessary.  This  method  of  stoping  and 
filling  in  deep  levels  will  be  found  a  great  improvement  on  some 
of  the  old  and  time-honored  practices  on  the  Mother  Lode  of 
California. 

In  some  mines,  if  stoping  be  expeditiously  carried  on  in  the 
manner  here  suggested,  no  filling  will  be  required,  the  timbers 
affording  all  the  support  to  the  walls  that  may  be  required;  but 
in  most  mines  filling  is  indispensable.  The  chambers  cut  to  supply 
filling  may  be  mined  either  by  hand  or  with  machines.  By  means 


182 


TIMBERING   AND   MINING 


of  a  lateral  foot-wall  drift  and  cross-cuts  a  large  section  of  the 
vein  may  be  completely  mined  in  a  few  months,  whereas  by  the 


FIG.  80.  —  Proposed  Method  of  Mining  and  Filling  from  the  Walls. 

old  methods  the  main  workings  must  be  kept  open  for  one,  two, 
or  three  years,  or  even  a  greater  length  of  time.  A  further  advan- 
tage, consisting  in  greater  expedition,  may  be  gained  by  cutting 


STOPING   IN   SWELLING   GROUND 


183 


an  inclined  raise  from  the  main  gangway  in  the  foot-wall  to  a 
point  about  midway  between  two  main  levels,  and  there  opening 
an  intermediate  level  (see  Fig.  80).  This  scheme  is  advisable 
where  the  ground  is  particularly  bad,  requiring  much  reinforce- 
ment of  timbers  and  renewals  as  well,  if  the  stope  is  to  be  kept 
open  very  long.  It  is  also  a  good  method  for  lessees  who  wish  to 
remove  as  much  ore  as  possible  within  a  given  period.  By  this 
method  the  ground  need  be  kept  open  only  about  half  as  long 
as  would  otherwise  be  necessary  if  the  stope  were  carried  up  from 


Stope 


FIG.  81.  —  Timbering  in  Stopes  at  the  Gwin  Mine 

the  main  level  only.  The  additional  expense  would  be  in  cutting 
a  series  of  inclined  raises,  each  about  45  to  50  ft.  long,  depending 
somewhat  on  the  dip  of  the  vein.  The  working  out  of  the  details 
in  each  particular  case  must  be  left  to  the  superintendent,  as  the 
conditions  at  no  two  mines  are  exactly  identical.  The  method 
proposed  appears  in  Fig.  80,  though  doubtless  subject  to  modi- 
fications and  possibly  to  improvements.  Fig.  81  shows  the  novel 
method  of  timbering  and  stoping  practised  at  the  Gwin  mine, 
where  the  walls  were  often  so  insecure  in  places  as  to  require  the 
unusual  method  of  timbering  shown. 


184 


TIMBERING  AND  MINING 


In  sinking  winzes,  it  is  an  excellent  idea  to  make  arrangements 
to  carry  the  track  several  feet  higher  than  the  floor  of  the  level, 
so  that  the  bucket  or  skip  may  be  dumped  automatically  into  a 
car  or  a  bin.  In  square-sets  the  track  can  be  continued  up  into 
the  second  set,  where  a  bin  could  be  built  provided  with  a  simple 
chute  for  drawing  the  rock  into  cars. 

Connecting  Levels  When  Sloping  Veins  of  Moderate  Width 
When  stoping  by  the  overhand  method,  on  approaching  the 


Sprag 


Track 


FIG.  82 

floor  of  the  level  above  it  is  necessary,  where  posts  and  caps  (the 
usual  drift  set)  have  been  used,  whether  sills  were  employed  or 
not,  to  take  some  precaution  to  prevent  the  falling  out  of  those 
timbers  and  the  caving  of  the  filled  stope  above.  At  the  Bi- 
Metallic  mine,  near  Phillipsburg,  Montana,  an  expeditious  and 
safe  method  was  introduced  (see  Fig.  82).  When  ready  to  break 
through  the  floor  under  any  particular  set  of  timbers  in  the  gang- 
way above,  a  sprag  was  placed  between  the  posts,  a  few  inches 
above  the  floor,  at  A,  and  there  tightly  secured  with  shingle 


STOPING   IN   SWELLING   GROUND 


185 


wedges.     A  heavy  stick  of   timber,  B  B,  long  enough  to  reach 
across  three  sets  (kept  on  each  level  of  the  mine  for  this  purpose) , 


I    I  n  n  n  I     l  rn  n   r 

Gap 


Bridge 


Sprag 


Sill 


FIG.  83.  —  Section  at  G.G. 

r-i  r-i    n 


Bridge 


I  n  n  n  I   I  n  n  n 


Cap 


FIG.  84  —  Section  at  D.H. 

was  lifted  to  the  roof  of  the  gangway,  midway  between  the  posts, 
one  end  being  beneath  the  cap  forming  a  part  of  the  set  about 
to  be  undermined.  This  timber  acts  as  a  lever,  having  a  fulcrum 


186  TIMBERING  AND  MINING 

at  C  in  the  post  which  supports  it,  the  foot  resting  in  the  center 
of  the  drift  on  a  sill  at  D.  Wedges  were  driven  in  tightly  at  E, 
and  also  at  F,  when  the  bottom  of  the  drift  at  G  could  be  removed 
with  safety  to  the  set  of  timbers  above  it,  only  the  sill  (if  there  were 
one)  dropping  out.  The  set  may  then  be  connected  securely 
with  the  timbers  in  the  stope  below.  This  excellent  scheme 
may  be  modified  to  suit  unusual  cases.  Figs.  83  and  84  illustrate 
sections  in  the  drift  at  G  G  and  D  H. 


CHAPTER  XXI 

STOPING   LARGE   ORE   BODIES 

IN  previous  chapters  have  been  described  at  considerable 
length  the  various  methods  ordinarily  employed  in  mining  veins 
and  ore  bodies  of  moderate  width,  and  the  various  methods 
described  are  those  principally  used  throughout  the  world.  Be- 
sides these,  however,  there  are  the  special  methods  required  for 
particular  cases,  where  the  low  dip  of  the  vein,  or  some  other 
physical  condition,  requires  such  methods.  Prior  to  1860,  veins 
under  20  ft.  in  width  that  required  artificial  support  of  some 
kind  were  rarely  mined  extensively,  though  many  attempts 
were  made  to  do  so,  usually  attended  with  disastrous  results 
and  generally  loss  of  life,  as  well  as  of  thousands  of  tons  of  ore. 
In  these  attempts  some  ingenious  schemes  were  introduced,  in- 
cluding splicing  of  long  timbers,  which  were  supported  at  inter- 
vals by  braces  or  sprags,  these  being  placed  longitudinally  with 
the  vein.  Notwithstanding  the  ingenuity  of  the  miners  and  the 
excellence  and  daring  of  the  schemes,  caves  followed  almost 
every  attempt.  Moreover,  the  expense  of  such  expedients  was 
in  most  instances  prohibitive.  When  the  mines  of  the  Comstock 
Lode  were  first  opened,  ore  deposits  of  unusual  width  were  found. 
Had  these  been  low  grade  and  had  they  offered  no  unusual 
inducement,  it  is  not  unlikely  that  the  tremendous  advances 
in  the  art  of  mining  that  then  came  into  existence  would  have 
been  delayed  for  many  years,  but  the  ore  deposits  of  the  Com- 
stock were  as  phenomenal  in  richness  as  they  were  in  size. 

The  following  interesting  reference  to  early  mining  on  the 
Comstock  is  from  Monograph  IV  of  the  United  States  Geological 
Survey,  "Comstock  Mining  and  Miners,"  by  Elliott  Lord:  "At 
the  50-ft.  level  [of  the  Ophir  Mine]  the  vein  of  black  sulphurets  was 
only  three  or  four  inches  thick,  and  could  readily  be  extracted 
through  a  drift  along  its  line,  propping  up  the  walls  and  roof, 
when  necessary,  by  simple  uprights  and  caps.  As  the  ledge 

187 


188 


TIMBERING  AND   MINING 


descended  the  sulphuret  vein  grew  broader,  until  at  a  depth  of 
175  ft.  it  was  65  ft.  in  width,  and  the  miners  were  at  a  loss  how  to 
proceed,  for  the  ore  was  so  soft  and  crumbling  that  pillars  could 
not  be  left  to  support  the  roof.  They  spliced  timber  together  to 
hold  up  the  caving  ground,  but  these  jointed  props  were  too  weak 
and  illy  supported  to  withstand  the  pressure  upon  them,  and  were 
constantly  broken  and  thrown  out  of  place.  The  situation  was 
a  curious  one.  Surrounded  by  riches,  they  were  unable  to  carry 
them  off.  The  company  was  at  a  loss  what  to  do,  but  finally 


FIG.  84  a.  —  Remarkable  Stope  Timbering  1250  Level  of  the  Elkhorn  Mine, 
Montana.     The  Roof  consists  of  Slate  which  is  Difficult  to  Hold. 

secured   the   services   of    Philip    Deidesheimer,    of    Georgetown, 
California,  who  visited  and  inspected  the  treasures  of  the  Ophir.'' 

Introduction  of  the  Square- Set  by  Philip  Deidesheimer  on  the 

Comstock 

That  the  ore  body  could  not  be  extracted  in  the  usual  manner 
was  at  once  apparent,  and  Mr.  Deidesheimer  told  the  writer  of 
this  treatise  that  he  set  about  his  task  with  some  misgivings. 
He  did  not  at  one  stride  grasp  the  idea  of  the  square-set,  but  the 


STOPING   LARGE   ORE   BODIES  189 

system  which  now  bears  his  name  was  the  outgrowth  of  circum- 
stances and  the  very  necessities  of  the  case.  He  instituted  a 
policy,  however,  the  wisdom  of  which  soon  became  apparent. 
The  first  step  was  to  cross-cut  the  vein  from  wall  to  wall,  starting 
from  a  drift  on  the  hanging-wall  side  of  the  vein.  As  the  work 
advanced  he  set  up  posts  and  placed  caps  above  them  — not 
across  the  course  of  the  drift,  as  usually  done,  but  along  the 
sides,  the  idea  being  to  form,  when  completed,  a  line  of  caps  that 
would  reach  continuously  from  wall  to  wall.  To  accomplish 
this  the  ends  of  two  caps  were  placed  upon  each  post,  except 
at  the  ends.  These  novel  sets  were  held  in  place  by  pieces  of 
2  X  4-in.  scantling  4J  ft.  in  length  and  reaching  across  the  drift 
from  near  the  top  of  a  post  to  that  opposite. 

Having  successfully  driven  the  cross-cut  Mr.  Deidesheimer 
now  ran  a  drift  some  distance  along  the  foot-wall,  timbering  with 
posts  and  caps  in  the  ordinary  manner;  that  is,  the  caps  were 
placed  upon  the  posts  at  right  angles  to  the  drift  and  parallel 
with  those  in  the  cross-cut.  The  posts  in  each  case  were  set 
vertically.  Returning  to  the  point  where  these  operations  were 
begun,  a  second  section  by  the  side  of  the  first  cross-cut  was  taken 
out  and  timbered  with  a  single  line  of  posts  and  caps,  the  2X4 
scantling  being  placed  as  in  the  first  case.  When  this  section  was 
completed  there  were  standing  three  rows  of  posts  surmounted 
by  three  lines  of  caps,  extending  from  the  foot  to  the  hanging- 
wall.  This  was  not  really  a  new  idea,  as  Mr.  Deidesheimer  had 
previously  employed  the  same  method  in  his  draft  mine  on  Forest 
Hill,  California,  where  the  breast  was  carried  125  ft.  wide,  the 
roof  being  supported  by  rows  of  posts  with  continuous  caps. 
The  work  thus  far  performed  in  the  Ophir  revealed  the  fact  that 
an  extremely  rich  body  of  ore  extended  upward  from  the  level 
where  this  work  had  been  done.  The  miners  were  directed  to 
commence  stoping  upward  in  the  body  of  soft,  black,  crumbling 
ore;  soon  a  considerable  excavation  had  been  made,  and  it  also 
became  evident  that  the  ground  must  be  secured  at  once. 

In  the  Georgetown  mine,  which  Mr.  Deidesheimer  had  left 
but  a  short  time  before,  the  vein  was  vertical,  and  the  walls  were 
so  soft  and  crumbling  that,  in  order  to  safely  stope  out  the  mineral, 
he  had  resorted  to  the  expedient  of  setting  one  post  directly  above 
another,  the  lower  end  resting  on  the  cap,  and  in  this  way  he 
managed  to  work  the  vein  without  much  difficulty.  (Compare 


190  TIMBERING  AND  MINING 

Fig.  81.)  The  Georgetown  experience  suggested  the  idea  of 
adopting  a  similar  plan  in  the  Ophir.  Accordingly,  Mr.  Deides- 
heimer  had  a  mortise  cut  at  the  junction  of  two  caps,  which  were 
already  in  place,  and,  having  a  post  framed  with  a  tenon  to  fit, 
set  the  post  directly  above  the  one  resting  on  the  floor  below. 
In  a  short  time  four  posts  were  in  position  with  the  caps  upon  them 
as  below,  together  with  the  frail  2X4  scantling,  the  office  of 
which  was  to  keep  the  other  timbers  from  falling  down.  The 
first  square-set  timbers,  it  will  be  seen,  were  framed  in  the  mine, 
the  mortises  being  cut  in  the  timbers  in  place.  The  work  of 
extracting  ore  proceeded  slowly  yet,  for  the  ground  had  to  be 
secured  as  well  as  possible.  It  soon  became  evident,  however, 
that  something  more  substantial  than  2X4  scantling  would  be 
required  to  keep  the  timbers  in  position,  and  it  was  determined 
to  put  in  timbers  of  the  same  dimensions  as  those  forming  caps 
and  posts.  This  was  done  at  once,  and  the  square-set  was  com- 
plete in  principle,  though  not  in  detail.  The  caps  occupied  all 
the  space  on  top  of  the  posts,  leaving  no  resting-place  for  the 
ties,  which  had  to  be  supported  in  some  other  manner.  As  they 
were  looked  upon  as  simply  an  auxiliary  —  a  support  to  the  posts 
and  caps,  not  subjected  to  vertical  pressure  —  they  were  only 
required  to  be  held  in  position.  Accordingly,  a  quantity  of  iron 
spikes  were  made,  in  shape  somewhat  like  the  thumb,  having 
a  sharp  point  at  one  end,  the  other  end  having  a  face  three-fourths 
of  an  inch  square.  Two  of  these  spikes  were  driven  into  a  post 
at  the  proper  height,  and  two  in  the  post  opposite,  the  ends  pro- 
jecting, and  the  tie  placed  so  that  the  ends  rested  upon  these 
iron  lugs,  wedges  being  driven  in  at  the  ends  to  secure  firmness. 
The  posts  and  caps  were  now  framed  on  the  surface  and  delivered 
below,  ready  for  use  whenever  needed.  The  work  of  mining  now 
progressed  much  more  rapidly  and  the  problem  seemed  solved. 
Soon  after,  it  was  determined  to  frame  the  timbers  so  that  the 
ties  might  also  rest  on  the  posts;  and  the  stopes  becoming  of 
great  size,  the  dimensions  of  the  timbers  were  increased. 

As  the  work  progressed,  slight  changes  were  made  from  time 
to  time,  whenever  any  improvement  seemed  possible.  Sills  were 
laid  on  the  floors  of  the  levels  as  a  foundation  for  the  timbers  above, 
which  had  now  assumed  massive  proportions.  The  sill  timbers 
were  as  long  as  it  was  possible  to  get  into  the  mine.  The  men 
who  were  obliged  to  handle  these  ponderous  timbers  could  see 


STOPING  LARGE  ORE  BODIES  191 

no  reason  why  the  sills  should  be  longer  than  the  caps,  and  had 
from  the  first  looked  upon  the  growth  of  this  new  system  with 
much  prejudice.  When  the  great  stopes  were  carried  up  from 
level  to  level  and  connected,  the  wisdom  of  the  use  of  long  sills 
became  apparent,  as  they  permitted  the  removal  of  all  the  ore 
and  the  placing  of  timbers  without  danger  or  loss,  which  could 
not  have  been  accomplished  with  short  sills,  as,  when  breaking 
up  through  the  floor  of  a  level  from  below,  short  sills  would  have 
had  nothing  to  sustain  them,  and  their  use  would  have  greatly 
increased  the  danger.  When,  in  the  course  of  ore  extraction, 
the  work  reached  the  walls,  additional  timbers,  called  "  wall 
plates,"  were  put  in.  The  caps  were  extended  from  the  nearest 
post  to  the  wall  plate,  except  when  a  post  came  within  two  feet 
of  the  wall  plate.  In  such  a  case  the  cap  extended  from  the  wall 
plate  to  the  second  post  in  a  single  piece. 

Usefulness  of  the  Square-Set  in  Extracting  large  Ore  Bodies 

Timbering  mine  excavations  with  square-sets  has  become  a 
world-wide  practice  since  the  days  of  1860,  when  Philip  Deides- 
heimer  introduced  the  method  in  the  Ophir  mine.  Prior  to  that 
time  there  was  no  method  known  to  miners  whereby  large  ore 
bodies  might  be  safely  mined  and  the  walls  and  roofs  of  stopes 
supported.  Mr.  Deidesheimer  soon  recognized  the  weak  points 
in  his  system  and  corrected  them  as  fast  as  they  developed.  He 
spared  no  expense  to  make  his  system  perfect,  or  as  nearly  so  as 
possible,  and  it  is  safe  to  say  that  the  Ophir  mine  was,  early  in 
the  sixties,  the  most  elaborately  timbered  mine  in  the  world. 
The  Ophir  timbering  omitted  nothing  calculated  to  make  a  com- 
plete and  enduring  system  of  support.  It  comprised  sills  on  the 
floor  of  each  level,  posts,  caps  and  ties.  These  timbers  are  common 
to  all  complete  square-set  systems,  but  the  Ophir  system  included, 
in  addition,  wall  plates  and  angle-braces,  which  were  inserted 
diagonally  between  the  sets  as  shown  in  the  illustrations  (Figs. 
85  and  86),  and  were  for  the  purpose  of  strengthening  the  system 
and  'affording  a  more  direct  means  of  resisting  the  thrust  due  to 
the  downward  weight  of  the  hanging-wall,  as  it  is  impracticable 
to  employ  the  square-set  system  in  any  other  manner  than  by 
setting  the  posts  upright  and  the  caps  and  girts  horizontally. 
Of  course,  the  posts  will  receive  any  pressure  coming  vertically 
from  above,  but  owing  to  the  usual  slope  of  the  hanging-wall, 


192 


TIMBERING  AND   MINING 


FIG.  85 


FIG.  86.  —  Details  of  Timbering  in  the  Ophir  Mine,  Comstock  Lode 


STOPING  LARGE  ORE   BODIES  193 

at  an  angle  to  the  horizon,  it  is  impossible  for  either  posts  or  caps 
to  directly  take  this  diagonal  thrust,  due  to  the  weight  or  settling 
of  the  hanging-wall;  consequently  the  angle-braces  were  intro- 
duced into  the  system.  Theoretically,  the  angle  at  which  the 
braces  are  placed  must  be  determined  by  the  angle  of  slope  of 
the  hanging-wall,  and  this,  in  turn,  would  determine  the  relative 
height  of  posts  to  distance  between  them.  As  the  angle  of  dip 
of  any  vein  wall  is  seldom  constant  over  large  areas,  it  at  once 
becomes  evident  that  uniformity  in  the  dimensions  of  timber 
sets  would  sooner  or  later  be  disturbed  by  a  change  in  dip  in  the 
walls,  this  necessitating  a  change  in  the  dimensions  of  the  system. 
When  such  a  change  is  made,  the  symmetry  of  the  system  is  at 
once  destroyed,  for  the  sets  will  no  longer  meet  in  making  con- 
nections from  one  stope  to  another  and  the  uniformity  so  necessary 
to  the  success  of  the  system  is  lost.  . 

Early  in  the  history  of  square-setting  these  facts  were  observed 
and  the  clever  miners  of  those  earlier  days  endeavored  to  meet 
the  exigencies  of  the  case  by  increasing  the  size  of  timbers  and 
reinforcing  the  sets  by  placing  angle-braces,  and  often  by  adding 
auxiliary  posts  or  caps  to  the  sets,  placing  them  at  the  side  of 
the  original  posts  and  beneath  and  above  the  original  caps. 
This  method,  when  introduced,  indicated  a  desperate  situation, 
but  could  be,  at  best,  only  a  makeshift,  for  ground  so  heavy  that 
such  elaborate  reinforcement  of  the  timber  sets  became  necessary 
could  not  be  held  by  any  system  of  timbering  short  of  solidly 
filling  the  stope  with  timbers,  which  expedient  has  actually  been 
resorted  to  in  a  few  cases.  Cribs  of  solid  timber,  and  cribs  filled 
with  waste  rock,  early  became  features  of  the  square-set  system. 

Mistakes  Made  in  Using  the  Square-Set 

From  the  beginning,  however,  the  worth  of  the  square-set 
system  was  everywhere  recognized,  and  it  was  promptly  adopted 
throughout  the  West.  Comstock  miners  went  abroad  and  in- 
troduced the  system  in  other  lands.  W.  H.  Patton,  a  Comstock 
miner,  took  the  idea  with  him  to  Australia  and  first  introduced 
it  there  in  the  Broken  Hill  mines  of  New  South  Wales.  Mining 
men  everywhere  adopted  it,  but  at  the  same  time  they  considered 
Mr.  Deidesheimer's  system  unnecessarily  elaborate  and  expen- 
sive and  began  to  dispense  with  various  portions  of  it.  The 
wall  plates  were  the  first  to  be  omitted,  then,  in  many  places,  it 


194  TIMBERING  AND   MINING 

was  found  the  angle-braces  could  be  left  out.  In  some  cases  the 
sills  were  omitted,  and  still  the  great  system,  reduced  as  it  was, 
admitted  of  the  removal  of  large  blocks  of  ore  with  apparent 
safety.  It  was  not  long,  however,  before  the  limitations  of  safety 
were  stretched  to  the  utmost,  and  usually  exceeded.  Enormous 
stopes  were  excavated  in  great  veins,  and  the  holes  were  filled  with 
an  elaborate  system  of  timbering,  comprising  posts,  caps  and  ties. 
In  some  instances  the  sets  were  not  properly  spragged  to  the  walls 
or  to  the  roof,  while  in  nearly  every  instance  where  the  square-set 
method  was  introduced,  the  grave  mistake  was  made  of  attempt- 
ing to  remove  too  large  a  superficial  area  of  ground  at  one  time. 
The  natural  result  followed;  disastrous  caves  occurred  in  nearly 
every  great  mine  where  the  square  system  was  employed. 

It  became  evident  that  something  more  was  required  to  per- 
fect the  method.  It  is  a  matter  worth  noting  that  the  great 
stope  in  the  Ophir  mine,  on  the  Comstock,  excavated  and  tim- 
bered under  the  personal  direction  of  Philip  Deidesheimer,  did 
not  cave.  His  system,  considered  by  many  to  be  unnecessarily 
elaborate,  at  least  held  the  ground  until  he  had  excavated  a 
stope  400  ft.  high,  from  60  to  over  100  ft.  wide  and  several  hun- 
dred feet  in  length.  This  was  an  immense  open  stope,  probably 
the  largest  in  the  world  at  the  time.  It  was  filled  after  reaching 
the  dimensions  indicated,  but  it  is  highly  improbable  that  this 
immense  hole  could  have  been  made  and  kept  open  as  long  as  it 
was  had  any  part  of  the  original  Deidesheimer  system  been  omitted. 
Had  either  wall  plates  or  angle-braces  or  sills  been  left  out,  it  is 
believed  the  Ophir  stope  would  have  met  the  disastrous  fate  of 
so  many  others.  The  secret  lay  in  carefully  preventing  the  ground 
from  starting.  Once  the  ground  gets  a  start,  and  it  begins  to 
"work,"  the  difficulties  of  holding  it  are  greatly  increased,  and  it 
is  rarely  that  the  placing  of  additional  timbers  in  the  stope  will 
avert  the  threatened  disaster.  We  have  knowledge  of  a  number 
of  cases  where  this  was  attempted,  and  in  each  instance  the 
cave  occurred,  the  timber  supports  being  entirely  unequal  to 
the  emergency  of  holding  up  great  masses  of  heavy  ground. 

The  square-set  system  is  sound  as  originally  designed;  it  is  the 
various  modifications  of  the  complete  system  that  are  at  fault. 
The  omission  of  important  features  is  disastrous  to  the  general 
scheme.  However,  it  was  long  since  learned  by  expensive  ex- 
perience that  heavy  ground  cannot  be  held  by  any  system  of 


STOPING   LARGE  ORE  BODIES  195 

timbering  if  the  excavation  be  of  large  size.  There  are  numerous 
instances  which  seem  to  contradict  this  statement,  where  large 
stopes  are  held  by  a  rather  light  system  of  square-sets,  but  care- 
ful examination  will,  in  these  cases,  generally  show  that  the 
ground  would  stand  nearly  as  well  with  no  timber  support  at  all. 
The  Yellow  Aster  mine  at  Randsburg,  California,  furnished 
excellent  examples  of  this  condition,  for  in  that  property  are 
stopes  several  hundred  feet  in  length,  over  100  ft.  wide,  and  more 
than  100  ft.  high,  timbered  with  square-sets  in  which  the  largest 
timbers  are  10  by  10  in.  If  the  hanging  country  were  to  settle 
on  these  frail  supports  they  would  not  resist  the  pressure  an 
hour.  In  fact,  several  caves  have  occurred  in  this  mine  where  the 
timber  sets  were  subjected  to  pressure.  Ground  stands  well  in 
all  desert  countries,  the  dry  atmosphere  greatly  reducing  the 
tendency  to  shift  and  cave.  In  the  Calico  mining  district  of 
California  are  huge  stopes  which  have  been  open  for  twenty 
years,  and  there  is  not  a  stick  of  timber  in  them.  The  rock  is 
rhyolite-tuff  and  tuffaceous  breccia,  and  while  it  is  easily  mined 
it  rarely  caves,  though,  of  course,  there  is  a  limit  to  the  extent 
to  which  even  that  excellent  standing  ground  may  with  safety 
be  excavated  without  support.  Experience  has  taught  that  the 
square-set  system  of  timbering  may  be  applied  to  the  excavation 
of  large  masses  of  ore,  but  that  the  excavations  must  be  restricted 
in  superficial  area,  that  the  stopes  after  timbering  must  be  filled 
as  the  work  progresses,  constantly  keeping  the  size  of  the  excava- 
tion within  the  limitations  of  safety. 

In  a  mine  at  Angels,  Calaveras  County,  California,  a  cave 
occurred  several  years  ago.  Report  said  that  the  stope,  which 
was  about  100  ft.  square,  had  been  carefully  timbered  with  mas- 
sive square-sets.  The  writer  had  an  opportunity  to  visit  this 
mine  soon  after  the  cave  and  went  through  the  portions  of  the 
stope  which  were  still  accessible.  The  great  timbers,  24  to  30  in. 
in  diameter,  had  been  split  and  broken  in  every  direction,  showing 
the  great  weight  of  the  rock  that  crushed  it.  The  superintendent 
said  that  "not  only  was  the  stope  timbered,  but  it  was  filled  as 
well."  This  statement  was  so  incompatible  with  the  fact  of  the 
disastrous  cave  that  had  occurred,  that  it  led  to  an  investigation 
of  the  condition  of  things.  It  was  found  that  the  stope  covered 
an  area  of  nearly  10,000  square  feet  —  about  100  feet  square.  It 
had  been  carried  up  a  little  over  four  sets  high  —  the  sets  were 


196  TIMBERING  AND   MINING 

8  ft.  high  and  the  back  was  from  2  to  6  ft.  above  the  upper  sets. 
The  hanging-wall  dipped  at  an  angle  of  about  75  to  80°,  the  foot- 
wall  being  somewhat  flatter,  but  consisting  of  several  feet  of 
talc  schist  —  a  most  excellent  lubricant.  Filling  had  been 
placed  in  the  stope  to  the  height  of  about  20  to  25  ft.  This 
brought  the  fill  to  within  12  to  15  ft.  of  the  back,  but  in  no  place 
did  it  touch  it.  Props  had  been  put  in  between  the  top  of  the 
sets  and  the  back,  and  also  reaching  from  the  sets  to  the  walls. 
The  great  mass  of  ore,  being  undercut  over  a  large  area,  began  to 
settle,  the  process  being  aided  by  the  talcose  walls,  and  a  cave 
resulted  as  a  natural  consequence. 

Filling  is  all-important,  but  it  must  be  placed  where  it  will 
afford  support  to  the  overhanging  rock,  or  it  fails  to  accomplish 
the  purpose  for  which  it  is  introduced  in  the  stope.  By  a  judi- 
cious combination  of  square-set  timbering  and  filling,  ore  deposits 
of  any  size  and  character  may  be  safely  extracted. 


CHAPTER  XXII 

FRAMING  SQUARE-SET  TIMBERS 

THE  framing  of  mine  timbers  is  an  operation  requiring  merely 
ordinary  skill  on  the  part  of  the  worl^nan.  Measurements  must 
be  made  with  care,  and  always  from  the  same  side  of  the  stick  of 
timber,  for  the  reason  that  large  timbers  of  stated  dimensions 
often  vary  from  \  to  J  in.  in  a  nominal  length  of  20  ft.,  and  some- 
times the  discrepancies  are  even  greater.  It  is  obvious  that  a 
stick  of  timber  20  ft.  long  which  is  12  X  12  in.  at  one  end  and 
Yl\  X  12}  in.  at  the  other,  must  be  framed  with  due  regard  to 
this  irregularity  in  cross-section  if  the  work  is  to  be  placed  uni- 
form, for  if  this  care  is  not  taken  it  will  quickly  result  in  bringing 
corners  out  of  line.  Ever  since  mining  began  and  timbers  were 
used  for  the  support  of  underground  workings,  all  timber  framing 
was  done  by  hand,  until  a  few  years  ago,  when  a  device  consisting 
of  a  gang  of  saws  was  introduced  to  frame  timbers  by  machine. 
These  timber-framing  machines,  simple  at  first,  have  been  im- 
proved until  to-day  they  have  reached  a  high  degree  of  perfection. 
Timbers  are  now  run  up  to  the  machine  on  a  truck  and  in  a 
moment  both  ends  are  completely  and  accurately  framed.  At 
any  large  mine  it  is  an  economy  to  use  a  timber-framing  machine, 
as  these  devices  perform  the  work  as  well  or  better  than  it  is 
generally  done  by  hand,  and  in  one-hundredth  part  of  the  time. 

The  framing  of  square-set  timbers  is  all  done  with  the  same 
object  in  view  — the  removal  of  small  sections  from  the  timbers 
in  such  a  manner  as  to  form  tenons  at  the  ends  of  the  individual 
sticks.  The  several  pieces  of  timber  making  up  the  system  are 
each  framed  differently,  yet  each  individual  piece  of  the  same  kind 
is  framed  in  exactly  the  same  way,  and  wherever  wanted  in  the 
mine  one  of  these  pieces  will  fit  in  without  alteration.  A  post  is  a 
post,  and  a  cap  is  a  cap,  and  if  a  post  or  a  cap  is  wanted  in  any 
part  of  the  mine  there  should  be  but  one  kind  of  post  or  cap  to 
send  to  the  workmen  at  the  place  where  it  is  wanted.  This  is 

197 


198 


TIMBERING  AND  MINING 


one  of  the  chief  advantages  of  the  Nevada,  or   Deidesheimer, 
square-set  system.     The  several  individual  pieces  going  to  make 


Cap 


Tie 


Tie 


Post 


Tie 


Cap 


Cap 


Post 


Cap 


Tie 


FIG.  87.  —  Method  of  Framing  for  Top  Pressure 


FIG.  88.  —  Framing  to  Resist  Side  Pressure 

up  the  complete  square-set  system  are  sills,  streak-sills,  posts, 
caps,  ties  (sometimes  called  girts),  wall  plates,  angle-braces, 
butt-caps,  cap-sills,  extension  caps,  sprags  and  —  by  no  means 


FRAMING   SQUARE-SET  TIMBERS 


199 


the  least  important  —  wedges,  for  without  the  simple  wedge  the 
entire  system  fails,  and  cannot  be  made  to  answer  any  useful 
purpose. 

Figs.  87,  88,  and  89  show  some  of  the  most  important  methods 
of  framing  square-set  timbers.  In  each  case  where  "square 
timber  "  is  employed,  the  post  is  actually  square  in  section,  though 
the  cap  and  tie  may  vary  from  this.  Very  frequently,  where 
the  post  and  cap  are  of  the  same  dimensions,  the  tie  is  2  in.  nar- 
rower than  the  cap,  though  of  the  same  depth.  The  object  of 
framing  the  timbers  is  to  permit  both  cap  and  tie  to  find  a  secure 


Tunnel  Cap 


View  of  Top 
End  of  Post 


Tunnel  Poat 

FIG.  89.  —  Round  Timber  Framed  by  Machine 

resting-place  on  the  shoulder  of  the  post.  As  the  tenon  is  only 
about  two-thirds  the  depth  of  the  cap  or  tie,  when  the  caps  and 
ties  are  in  place,  resting  on  the  shoulder  of  the  post,  a  mortise- 
like  depression  is  formed  on  top  of  the  post  which  is  equal  in 
depth  to  one-third  the  depth  of  the  cap.  In  this  mortise  the 
shorter  tenon,  framed  on  the  bottom  of  each  post,  is  set.  Fig.  87 
represents  the  method  of  framing  for  "down  pressure."  To  resist 
downward  pressure  the  timbers  are  framed  so  that  the  posts  butt 
directly  together,  the  top  of  a  lower  post  coming  into  immediate 
contact  with  the  bottom  of  that  next  above,  thus  forming  a  con- 
tinuous post  from  the  sill  to  the  top  of  the  stope,  or  to  a  connec- 
tion with  the  sills  of  the  level  above. 

Not  infrequently,  as  mining  proceeds,  it  is  observed  that  the 


200  TIMBERING   AND   MINING 

pressure  is  being  exerted  from  the  side  rather  than  from  overhead. 
In  such  an  event  it  is  the  practice  to  so  frame  the  timbers  that  the 
caps  form  a  continuous  line  from  foot  to  hanging  wall,  as  shown 
in  Fig.  88.  Fig.  89  shows  the  result  of  framing  round  timbers 
with  a  framing  machine.  In  some  mines  round  timbers  are  used 
exclusively,  in  square-setting  as  well  as  in  drifts  and  elsewhere. 
Undoubtedly,  round  timbers  are  better  than  those  that  have 
been  squared  by  saw.  No  round  timber  should  be  placed  in  a 


FIG.  89a.  —  Slope  in  a  Utah  Mine  showing  Combination  of  Round  and  Square 
Timbers  in  Square-Sets 

mine,  however,  without  first  peeling  off  the  bark,  This  should 
be  stripped  at  the  time  of  cutting,  in  order  that  the  timber  may 
season  properly.  In  some  mines  a  combination  of  round  and 
square  timbers  is  used  in  square-sets,  which  has  been  found  to 
work  well.  Notwithstanding  the  fact  that  the  round  timbers 
are  never  exactly  the  same  size,  the  framing  machine  removes 
all  inequalities  and  leaves  the  timbers  cut  uniform,  so  that  they 
are  interchangeable  even  with  square  timbers. 


FRAMING  SQUARE-SET  TIMBERS  201 

There  are  several  so-called  systems  of  framing  timbers  for 
square-setting  —  modifications  of  the  two  methods  here  illus- 
trated for  top  and  side  pressure  —  and  these  differ  from  those 
shown  only  in  the  manner  of  cutting  the  posts,  caps  and  ties. 
The  primary  idea  of  these  is  to  reduce  to  a  minimum  the  tendency 
of  the  timbers  to  split  under  pressure.  The  idea  is  all  right  in 
itself,  but  these  elaborately  framed  sets  resist  pressure  little  if 
any  better  than  those  framed  more  simply,  as  shown.  In  the 
earlier  years  of  the  square-set,  say  thirty  years  ago,  it  was  the 
practice  to  employ  square  timbers  the  dimensions  of  which  were 
18  X  18  up  to  24  X  24  in.,  but  even  these  massively  timbered 
stopes  caved.  On  the  "  Homestake  Belt "  in  the  Black  Hills, 
the  Father  de  Smet,  the  Deadwood,  the  Golden-Terra,  the  Cale- 
donia, the  Highland,  and  the  Homestake  mines  each  had  large 
stopes  filled  with  an  elaborate  square-setting  of  massive  timbers, 
and  yet  great  caves  occurred  in  every  one  of  these  mines.  Caves 
were  of  frequent  occurrence  on  the  Comstock,  in  the  mines  of 
Butte,  Montana,  and  at  almost  every  other  place  where  square- 
sets  without  filling  have  been  employed,  both  in  America  and 
abroad.  In  more  recent  years  the  tendency  has  been  to  reduce 
the  size  o£  timbers  and  to  fill  the  stopes  with  waste  as  rapidly  as 
possible.  The  timber  sets,  properly  employed,  make  it  possible 
to  do  this,  and  it  is  the  only  way  the  ore  can  be  safely  removed 
from  large  veins  where  the  square-set  system  of  timbering  alone 
is  depended  upon.  The  increasing  scarcity  of  timber  has  caused 
a  corresponding  increase  in  its  cost,  and  mine  managers  have 
therefore  sought  to  devise  some  method  of  mining  which  would 
admit  the  removal  of  large  masses  of  ore  in  safety  with  the  em- 
ployment of  a  minimum  of  timber  and  at  as  low  a  cost  as  possible. 
This  has  led  to  the  introduction  of  several  ingenious  schemes, 
designed  to  meet  particular  requirements. 

Construction  of  the  Square- Set  in  the  Stope 

The  basis  of  the  square-set  system  of  timbering  is  the  sills. 
These  are  placed  on  the  floor  of  the  stope  and  upon  them  is  built 
the  superstructure  of  posts,  caps  and  ties.  A  system  that  is 
complete  in  its  details  includes  not  only  the  lower  or  mud-sills, 
but  sills  running  at  right  angles  to  these,  known  as  streak-sills  or 
girders.  It  is  upon  these  latter  that  the  posts  are  placed.  In 
many  mines  the  girders  are  dispensed  with  and  sprags,  or  tie- 


202  TIMBERING  AND  MINING 

sills,  are  employed  in  their  stead.  Generally  speaking,  these 
latter  fulfil  every  requirement.  In  such  a  case  the  posts  set  on 
the  mud-sills.  The  chief  reason  for  placing  the  sills  is,  not  to 
form  a  base  upon  which  to  build  the  sets,  but  to  provide  a  safe 
means  of  connecting  one  level  with  the  next  above.  Where  sills 
have  been  omitted,  much  difficulty  has  been  encountered  later 
in  making  connection  between  levels.  As  this  is  the  main  func- 
tion of  sills,  it  is  apparent  that  sills  should  be  as  long  as  consistent 
with  convenience  in  handling  —  at  least  the  length  of  two  sets, 
three  is  better,  so  that  when  breaking  through  from  below,  the 
sets  of  the  stope  above  may  be  held  securely  until  connection 
can  be  made  between  the  timbers  of  the  two  stopes.  This  per- 
formance, of  course,  assumes  that  the  work  is  taken  up  in  small 
sections.  Over  the  sills  should  be  laid  a  floor  of  old  timbers, 
lagging,  and  similar  pieces  of  lumber  to  hold  filling,  or  ore,  as  the 
case  may  be. 

In  starting  a  stope,  when  sufficient  ground  has  been  broken 
to  afford  the  necessary  room,  the  sills  should  be  laid,  their  posi- 
tion having  been  properly  determined  by  the  mine  surveyor, 
with  reference  to  the  sills  in  the  stope  above,  which  will  be  of 
advantage  when  the  time  arrives  to  connect  the  two  levels. 
Where  girders  are  dispensed  with,  the  sills  are  laid  at  right  angles 
to  the  strike  of  the  vein  —  from  foot  to  hanging  —  the  same  as 
the  caps.  At  a  certain  distance  from  the  wall,  or  at  a  point 
determined  by  the  mine  surveyor,  a  dap  1  in.  deep  is  cut  in  the 
sill  to  receive  the  post,  and  at  regular  intervals  other  daps  are 
cut,  the  distance  apart  being  determined  by  the  dimensions  of 
the  system,  usually  5  ft.  from  center  to  center  of  the  posts.  The 
height  of  posts  on  the  sill  floor  is  often  greater  than  that  of  those 
above,  in  order  to  give  the  necessary  head  room.  In  wet  mines, 
too,  provision  is  often  made  for  drainage  by  giving  the  sill  floor 
the  necessary  grade  toward  the  shaft  or  toward  some  other  drain- 
age point,  the  sills  conforming  to  this  established  grade,  while 
the  first  set  of  caps  above  will  be  laid  level.  This  makes  the  posts 
of  the  sill  floor  shorter  as  the  stope  proceeds  away  from  the  point 
of  drainage.  In  most  mines,  however,  no  attention  is  paid  to 
such  refinements  of  practice,  as  the  very  slight  tilt  given  the  timber 
sets  by  the  grade  of  the  floor  is  negligible  in  considering  stress. 

When  sufficient  space  has  been  made  on  the  sill  floor,  and  a 
double  line  of  sills  laid,  the  first  four  posts  are  placed  in  position 


FRAMING  SQUARE-SET  TIMBERS  203 

and  held  there  temporarily  by  nailing  light  braces,  such  as  2  X 
6-in.  scantling,  or  a  strip  of  lagging,  to  them.  The  caps  are  then 
lifted  to  place  and  similarly  secured  temporarily,  when  the  ties 
are  put  in.  As  soon  as  the  first  four  posts,  two  caps  and  two  ties 
are  in  position,  they  are  spragged  to  the  surrounding  rock  —  sides 
and  top  —  and  made  as  tight  as  possible  by  wedging.  If  the 
shooting  is  heavy  and  the  timbers  small,  they  may  be  protected 
from  the  blasts  by  piling  old  timbers  in  front  of  them.  Not  in- 
frequently a  round  of  heavy  shots  will  knock  down  two  or  three 
sets  that  have  not  been  rendered  sufficiently  secure.  The  breast 
of  the  stope  may  be  carried  several  sets  wide  along  the  vein  — 
sometimes  extending  from  wall  to  wall,  if  the  vein  is  not  too  wide, 
but  in  very  wide  veins  (those  over  40  ft.)  it  is  the  better  practice 
to  carry  the  stope  from  foot  to  hanging.  In  fact,  the  block 
system  is  advised  in  all  cases,  and  experience  has  shown  that 
stopes  may  safely  range  from  40  to  60  ft.  wide,  depending  on  the 
character  of  the  ground. 

When  the  stope  has  become  several  sets  wide  and  long,  sto- 
ping  may  be  carried  upward.  Sometimes  it  is  necessary  at  first 
to  build  temporary  platforms  between  the  sets  to  bring  the  men 
within  drilling  reach  of  the  ground,  but  as  stoping  proceeds 
upward,  an  effort  is  made  to  break  the  ground  in  such  a  manner 
that  it  will  be  unnecessary  to  build  platforms.  An  experienced 
foreman  will  see  that  the  machines  are  set  and  the  holes  drilled 
so  that  after  blasting  there  will*  be  a  suitable  place  to  set  up  for 
the  next  round.  It  is  an  easy  matter  for  blundering  miners  to 
put  in  a  round  of  holes  which,  after  blasting,  may  leave  the 
back  too  high  to  be  conveniently  reached  without  building  cribs 
on  which  to  stand  while  drilling  the  next  round.  Throughout 
stoping,  when  the  men  work  on  the  timber  sets,  foresight  is  con- 
stantly necessary:  always  look  ahead  to  see  what  will  result  from 
a  contemplated  round  of  holes,  and  decide  what  shall  be  done 
next.  If  this  simple  precaution  be  not  taken,  much  of  the  time 
men  will  be  working  at  a  disadvantage. 

In  all  places  where  large  ore  bodies  are  to  be  extracted  and 
the  stopes  timbered  with  square-sets,  it  is  advisable  to  cut  raises 
from  the  sill  floor  of  each  stope  upward  to  the  floor  of  the  level 
above,  these  raises  to  be  lined  with  poles  or  plank  and  used  as 
timber  chutes  or  slides,  down  which  all  timbers  to  be  used  in  the 
stope  may  be  sent  from  the  level  above.  Machine  drills  and  other 


204  TIMBERING  AND  MINING 

heavy  articles  may  be  sent  down  through  these  chutes  also. 
These  timber  chutes  may  be  cut  much  flatter  than  those  cut  for 
the  passage  of  ore,  or  rock,  as  low  as  30°  being  permissible,  as  the 
timber  is  thrown  into  the  chute  from  a  timber  truck,  and  slides 
rapidly  down  to  the  floor  where  it  is  to  be  used.  If  the  stope  is 
carried  up  in  the  vicinity  of  the  raise,  so  that  the  topmost  floor 
connects  with  it,  timber  can  be  delivered  by  gravity  to  the  level 
of  any  floor  of  the  stope. 


CHAPTER  XXIII 

MODIFICATIONS  OF  THE  SQUARE-SET  SYSTEM  IN 
CALIFORNIA   MINES 

ALTHOUGH  the  square-set  system  of  timbering  is  based  upon 
well-recognized  principles,  these  principles  are  not  always  faith- 
fully followed.  Some  men  appear  to  believe,  judging  by  their 
work,  that  any  kind  of  arrangement  of  timbers  will  be  satisfactory 
and  will  answer  every  purpose.  It  is  this  erroneous  idea  that  has 
led  to  the  introduction  of  all  sorts  of  modifications  of  the  original 
idea  of  Philip  Deidesheimer.  Some  of  these  modified  systems 
are  very  strong,  and  do  hold  heavy  ground  as  well,  perhaps,  as 
any  other  system;  but  after  all  they  may  possess  no  advantage 
over  what  may  be  called  the  Standard  Deidesheimer  system 
while  they  may  include  elements  that  render  them  more  difficult 
of  construction,  requiring  more  men  and  more  time  to  put  in 
place.  Among  the  California  miners  who  usually  did  things 
"in  their  own  fashion,"  no  matter  what  others  did,  was  the  late 
Alvinza  Hayward.  That  gentleman  was  the  fortunate  owner  at 
one  time  or  another  of  several  of  the  largest  and  most  valuable 
gold  mines  in  California.  Among  them  were  the  Union  mine 
in  El  Dorado  County;  the  Empire  and  Pacific  (Plymouth  Con- 
solidated) and  the  Eureka  and  Badger  (Amador  Consolidated), 
in  Amador  County;  the  Utica-Stickle  mine  in  Calaveras  County; 
and  a  number  of  others;  but  each  of  those  mentioned  were  large 
and  rich  mines,  and  in  them  Mr.  Hayward  introduced  his  own 
methods.  These  methods,  while  differing  in  important  particu- 
lars from  those  in  common  use  elsewhere,  were  nevertheless 
satisfactory,  and  apparently  served  every  purpose.  However, 
we  believe  that  the  Hayward  systems  were  more  cumbersome 
than  the  Standard  system,  and  otherwise  objectionable  in  some 
of  their  features. 

One  of  the  main  departures  from  the  usual  practice  was  the 
placing  of  the  posts  directly  upon  the  rock  floor  of  a  level,  such  a 

205 


206  TIMBERING  AND  MINING 

thing  as  a  sill  never  being  employed.  The  posts  were  16  ft.  in 
height,  and  while  the  framing  was  essentially  similar  to  that  em- 
ployed in  the  Standard  system,  it  necessitated  the  wedging  in  of 
sprags  about  the  middle  of  the  posts,  8  ft.  above  the  floor.  The 
sets,  when  in  position,  were  very  strong,  being  made  up  of  posts 
24  to  30  in.  in  diameter,  and  caps  20  to  24  in.,  with  ties  12  to  24 
in.  diameter.  Such  huge  timbers  should  support  ground  if  any 
timber  would,  but  even  these  stopes  caved  occasionally  where  too 
large  an  area  was  stoped.  In  those  early  days  filling  was  not 
extensively  practised.  The  main  disadvantages,  however,  seem 
to  have  been  the  great  size  of  the  posts  and  the  corresponding 
difficulty  in  handling  these  great  logs  and  placing  them  in -posi- 
tion. Moreover,  the  system  required  a  stope  to  be  nearly  18  ft. 
high  before  these  great  posts  could  be  set  up,  and  in  many  places 
this  was  accomplished  with  danger,  owing  to  the  size  of  the  un- 
supported excavation  that  had  to  be  made  before  the  timber 
could  afford  any  support  to  it  whatever.  Of  course,  the  difficulty 
of  connecting  levels  was  not  simplified  by  the  omission  of  sills. 
In  time  the  practice  of  using  16-ft.  posts  was  discontinued  for 
8-ft.  posts,  which  at  once  made  the  Hayward  system  in  most 
respects  similar  to  the  Deidesheimer  system. 

In  the  Utica  mine,  at  Angels,  another  modification  of  the 
square-set  system  was  introduced,  and  this  was  followed  to  some 
extent  by  other  mines  on  the  Mother  Lode.  Strange  as  it  may 
seem,  not  a  mine  on  the  Lode,  with  its  great  bodies  of  ore,  where 
square-setting  was  commonly  employed,  made  use  of  sills  prior 
to  1893.  At  that  time,  or  in  the  following  year,  sills  were  first 
introduced  in  the  Utica  mine,  but  few  of  the  other  mines  followed 
the  example  of  the  Utica.  It  was  claimed  that  the  sills  would  be 
of  no  use,  as  they  would  rot  and  become  useless  before  the  levels 
were  connected.  This  was,  in  most  cases,  true,  owing,  as  previ- 
ously explained,  to  the  method  of  working  these  mines.  The 
veins  or  ore  bodies  were  often  of  great  size  — 100  ft.  or  more  in 
width  —  while  the  milling  plant  was  generally  small,  consisting 
usually  of  40  to  120  stamps.  A  body  of  quartz  100  ft.  high, 
100  ft.  wide,  and  100  ft.  long  contains  nearly  80,000  tons.  A 
40-stamp  mill  crushing  3000  to  4000  tons  a  month  could  run 
steadily  on  this  mass  of  ore  for  two  years  or  more,  and  as  stoping 
was  generally  progressing  on  several  levels  at  one  time,  it  required 
several  years  to  carry  up  one  of  these  great  stopes  of  large  section 


SQUARE-SET  SYSTEM   IN   CALIFORNIA  MINES 


207 


from  one  level  to  the  next  above,  during  which  time  the  sills 
had  ample  time  to  rot  and  become  useless. 

The  old  methods  of  mining  in  most  of  the  great  Mother  Lode 
mines  are  antiquated,  and  although  cheap  for  the  time  being, 
were  not  the  best  when  the  economy  of  the  future  is  considered. 
Each  manager  sought  to  stope  his  best  ore  and  to  make  a  large 
output.  The  result  was  large  excavations,  generally  without 
filling,  and  ultimately  caves,  with  the  attendant  expense  and 
danger  of  recovering  such  ore  as  could  be  drawn  from  the  caved 


W&fflf'sK 

FIG.  90.  —  Use  of  the  Cap-Sill  in  Square-Sets 

ground.  In  some  mines  the  posts  have  been  set  up  from  8  to 
16  ft.  in  height  and  the  caps  placed  on  top  of  them,  completely 
covering  the  top  of  the  post,  while  no  framing  was  done  to  receive 
the  foot  of  the  post  of  the  next  set  above.  This  necessitated 
much  work  with  ax  and  adz  in  the  stope,  something  which  should 
be  avoided  as  far  as  possible.  In  other  mines  the  ties  or  sprags 
have  been  omitted,  probably  with  a  view  to  economizing  timber 
and  time,  but  this  does  not  look  like  real  economy,  for  if  the 
ground  shifts  slightly,  the  timber  sets  are  very  likely  to  ride 
sideways  and  "jackknife,"  as  the  miners  call  it,  causing  complete 


208  TIMBERING  AND   MINING 

collapse.  When  heavy  standard  square-sets  do  this  under  unequal 
pressure,  it  is  scarcely  to  be  expected  that  a  system  of  timber- 
ing from  which  important  members  are  missing  will  do  any  better 
under  similar  circumstances. 

The  great  variation  in  the  angle  of  dip  of  the  walls  of  ore  de- 
posits and  veins,  as  well  as  in  the  character  of  the  walls  or  sur- 
rounding rocks,  often  necessitates  the  introduction  of  special 
methods  of  timbering,  such  as  are  illustrated  in  the  accompanying 
sketch,  Fig.  90.  In  this  case  the  foot-wall  was  too  soft  (talc 
schist)  to  afford  firm  support  to  the  foot-wall  posts,  and  in  con- 
sequence the  miners  were  obliged  to  cut  deep  hitches  in  the  foot- 
wall  rock  in  order  to  secure  a  firm  footing  for  posts,  but  the 
particular  feature  of  this  case  is  the  introduction  of  what  is  called 
the  "cap-sill."  It  is  at  once  apparent  that  this  is  most  useful, 
wherever  it  may  be  necessary  to  meet  such  conditions  as  are 
described.  The  name  "cap-sill"  indicates  the  peculiar  function 
of  this  member  of  the  square-set  system  of  timbering.  Cap-sills 
may  be  introduced  in  the  timbering  of  small  stopes  as  well  as 
in  those  of  large  size. 

Among  the  large  mines  of  the  West,  where  round  timbers  are 
exclusively  employed  in  supporting  stopes,  is  the  Utica-Stickle 
mine,  at  Angels,  Calaveras  County,  California.  The  main  ore 
body  worked  in  this  property  ranged  from  40  to  120  ft.  in  width, 
was  more  than  1000  ft.  long,  and  about  400  ft.  high.  The  for- 
mation is  amphibolite  schist,  which  on  the  foot-wall  side  is  altered 
to  soft  talc,  often  wet,  and  several  feet  in  thickness.  Generally, 
the  hanging-wall  is  solid,  but  often  came  away  in  great  slabs 
weighing  many  tons.  Obviously,  the  stoping  of  this  great  mass 
of  ore,  which  stood  at  an  angle  of  nearly  80°  on  the  hanging 
side,  but  with  greatly  varying  dip  on  the  foot,  required  much 
skill  and  ingenuity  on  the  part  of  the  mine  management,  as  it 
involved  no  little  danger.  The  accompanying  sketches,  Figs. 
91  and  92,  will  give  an  idea  of  the  method  of  timbering  employed 
in  the  Utica-Stickle  mine.  The  timber  used  is  round,  peeled 
pine  logs,  delivered  under  contract  at  the  mine.  I  have  been 
informed  that  the  cost  of  these  logs  was  10  cents  for  each  inch  in 
diameter,  for  a  16-ft.  log.  Thus  a  20-in.  log  would  cost  $2,  while 
one  24  in.  in  diameter  would  cost  $2.40.  The  timbers  are  mostly 
over  18  in.  diameter  and  are  as  large  as  24  and  even  30  in.  Sprags 
are  mostly  12  to  16  in.  diameter.  The  larger  timbers  are  all 


SQUARE-SET  SYSTEM   IN   CALIFORNIA   MINES  209 


V  r', 

'///A      'I™, 


FIG.  91.  —  Utica  Method  of  Square-Setting.     (Cross-Section) 


210 


TIMBERING   AND   MINING 


sawed  into  8-ft.  lengths  and  framed  by  machine,  the  tenons  being 
14  inches  square,  top  and  bottom,  and  4   in.  long.      Caps  are 


FIG.  92.  —  Utica  Method  of  Square-Setting.     (Longitudinal  Section) 

framed  to  14  in.  square,  the  "horn"  being  6  in.  long.  It  will  be 
observed  that  when  the  caps  are  placed  on  the  posts,  the  tenons  or 
horns  fail  to  meet  by  2  in.  This  space  is  filled  with  a  piece  of 


SQUARE-SET  SYSTEM   IN   CALIFORNIA  MINES  211 

2-in.  plank  14  in.  square.  Some  years  ago  the  men  became  rather 
careless  in  setting  up  these  timbers,  and  in  at  least  one  stope 
the  2-in.  plank  was  omitted,  with  the  result  that  when  pressure 
was  exerted  the  caps  gradually  butted  together  and  the  hanging- 
wall  settled,  many  heavy  slabs  falling  and  causing  numerous 
accidents  as  well  as  much  additional  expense  to  hold  the  ground, 
which  should  never  have  been  allowed  to  start. 

At  the  junction  of  caps  and  posts  it  will  be  observed  that  two 
sprags  (ties)  are  introduced  to  hold  the  upper  and  lower  post  in 
position  independently.  The  sprags  are  4  ft.  long,  the  lower  one 
being  framed  with  a  horn  4  in.  in  length,  as  shown,  on  its  upper 
half.  These  projections  rest  upon  the  shoulders  of  the  post, 
while  the  upper  sprag  is  tightly  wedged  between  the  posts.  In 
this  mine  the  caps  and  posts  often  weigh  700  to  over  1000  lb.,  and 
the  timber  gang  is  made  up  .of  powerful  men  who  are  able  to  handle 
these  great  logs  with  comparative  ease.  The  timbers,  when  in 
place,  form  a  very  heavy  and  strong  system  of  support,  but 
seems  to  possess  no  advantages  over  the  standard  sets.  Owing 
to  the  impossibility  of  procuring  round  timbers  that  are  uniform 
in  diameter,  ihis  system  involves  a  great  amount  of  work  in  the 
mine,  dressing  timbers  with  ax  and  adz  making  a  great  quantity 
of  chips,  which  later  prove  a  nuisance  in  the  mill. 

At  the  Wildman  mine  at  Sutter  Creek,  Amador  County,  Cali- 
fornia, the  method  of  timbering  is  similar  to  that  at  the  Utica. 
The  posts  are  provided  with  tenons  6  X  12  in.,  which  are  8£  in. 
long  on  the  upper  ends  and  3J  in.  long  on  the  lower  ends.  The 
posts  abut  upon  each  other,  the  caps  being  framed  with  a  tenon 
12  X  12  in.  and  4  in.  long.  These  tenons  rest  upon  the  shoulders 
of  the  posts.  Double  sprags  are  also  in  use  at  the  Wildman, 
but  are  placed  side  by  side,  so  as  to  catch  the  two  caps,  instead  of 
one  above  the  other,  as  in  the  Utica  system.  In  the  Wildman 
mine  the  timbers  are  generally  smaller  than  those  used  at  the 
Utica,  being  from  14  to  18  in.  diameter. 

Construction  of  Chutes  in  Square-Sets 

In  most  mines  employing  the  square-set  system  of  timbering 
ore  chutes  are  built  in  the  sets  of  the  sill  floor  for  the  purpose  of 
drawing  off  the  ore  broken  in  the  floor  above.  When  the  excava- 
tion has  proceeded  sufficiently  to  admit  of  the  timbers  being 
carried  two  sets  high,  tracks  may  be  laid  wherever  desired  on  the 


212  TIMBERING  AND   MINING 

sill  floor,  and  ore  bins  built  in  the  timber  sets,  with  chutes  arranged 
along  the  car  tracks  at  convenient  intervals  in  order  that  cars 
run  beneath  the  chutes  may  be  expeditiously  filled.  It  is  the 
usual  practice  to  lay  a  heavy  bulkhead  on  the  upper  floor  of  the 
sets,  so  that  when  blasting  the  rock  may  fall  on  the  bulkhead, 
where  it  can  be  broken  up  with  hammers  to  a  size  that  will  readily 
pass  the  chute  doors.  If  the  ore  is  not  drawn  off  from  the  bins 
as  fast  as  broken,  the  bins  will  soon  be  filled  to  the  top,  when  the 
ore  may  be  blasted  down  directly  upon  the  broken  ore,  where 
the  large  pieces  may  be  reduced  to  the  desired  size.  The  ore  pro- 
tects the  timbers  of  the  set,  and  the  bulkheads  become  no  longer 
necessary.  Where  large  stopes  are  completely  filled  with  square- 
sets,  however,  this  scheme  of  carrying  a  large  amonut  of  ore  in 
the  bins  is  not  the  best  practice,  as  it  exerts  too  much  weight 
on  the  timbers  adjacent  to  the  bins,  while  there  is  no  correspond- 
ing weight  elsewhere,  which  sometimes  displaces  timbers  and 
throws  the  sets  out  of  line. 

The  difficulties  encountered  in  the  endeavor  to  lessen  the  cost 
of  extracting  large  ore  bodies  have  been  numerous,  and  many 
novel  schemes  have  resulted.  There  has  been  a  growing  tendency 
to  reduce  the  amount  of  timber  required  in  mining  large  ore  bodies, 
and  in  many  instances  these  efforts  have  met  with  success.  In 
others  the  amount  of  timber  used  is  so  small  as  to  be  almost 
negligible. 


CHAPTER  XXIV 

STOPING  LARGE  ORE  BODIES  BY  THE  BLOCK  SYSTEM 
AT  BROKEN  HILL,   NEW  SOUTH  WALES 

ONE  of  the  great  lodes  of  the  world  is  that  at  Broken  Hill, 
New  South  Wales.  It  is  a  huge  deposit  of  lead-silver  ore,  with 
much  iron,  zinc  and  copper  sulphide.  The  lode  is  situated  in  the 
Barrier  Range  of  mountains,  and  at  the  time  of  its  discovery 
was  many  miles  from  the  nearest  settlement  and  about  ninety 
miles  from  the  nearest  railway,  in  the  midst  of  a  desert  not  unlike 
that  of  Southern  California.  The  richness  of  the  ores  quickly 
brought  Broken  Hill  into  the  foremost  rank  of  great  mines,  and 
millions  of  dollars  in  precious  and  base  metals  have  been  taken 
from  the  great  lode.  As  in  other  great  lodes,  the  early  mining 
operations  were  conducted  with  a  view  to  realizing  promptly 
the  greatest  possible  profit  and  with  little  regard  for  the  future. 
The  result  is  that  mining  at  Broken  Hill  is  to-day  dangerous, 
and  owing  to  the  high  cost  of  timber  and  labor  new  methods 
were  devised  several  years  ago  to  work  the  caving,  shifting  ground 
with  as  great  assurance  of  safety  as  it  was  possible  to  secure,  and 
at  the  same  time  extract  the  ore.  . 

Edwin  K.  Beaumont  has  described  the  mining  methods  at 
Broken  Hill  in  the  "Transactions  of  the  Australian  Institute  of 
Mining  Engineers,"  from  which  the  following  is  abstracted: 
"The  impressions  of  a  new  arrival  on  coming  to  the  Barrier  are 
anything  but  pleasant  or  reassuring,  for  when,  after  spending  a 
whole  night  in  rattling  over  300  miles  of  almost  desert  country, 
one  seeing  the  line  of  lode,  about  one  and  one-half  miles  in  length, 
with  its  long  chain  of  chimney  stacks,  poppet  heads,  engine 
houses,  concentrating  mills,  and  immense  mullock  and  tailings 
dumps,  etc.,  finds  it  hard  to  imagine  that  this  is  the  famed  Barrier 
Range  or  Broken  Hill,  unless  one  is  a  mining  man  who  has  been 
on  similar  fields.  The  original  Broken  Hill  is  now  a  thing  of  the 
past,  having  been  entirely  removed  by  the  large  open  cuts,  from 
which  the  oxidized  ore  is  being  extracted  down  to  from  200  to 

213 


214  TIMBERING  AND  MINING 

250  ft.  The  story  of  the  finding  of  silver  by  the  stockman  on 
Mount  Gipps  station  and  of  Rasp's  shaft  (Rasp  himself  being  a 
station  hand  at  the  time),  and  of  the  mining  of  earlier  years,  are 
familiar,  when  only  the  oxidized  ores  of  the  upper  levels  of  the 
lode  were  worked  down  to  300  or  400  ft.,  and,  as  on  new  fields, 
the  methods  adopted  were  crude,  until  with  great  advance  of  out- 
put and  rush  of  population,  more  modern  and  advanced  systems 
were  adopted,  upon  the  arrival  of  American  mining  managers  and 
engineers  with  the  square-set  system  of  timbering,  as  carried  out 
in  ore  mines  of  America  and  elsewhere. 

"In  mining  these  large  ore  bodies  the  square-set  system  is 
employed.  This  method  of  mining  was  introduced  on  the  Lode 
by  W.  H.  Patton,  an  American  mining  engineer,  and  an  old 
Comstocker.  The  timbers  are  framed  in  the  usual  manner  by 
machines  in  the  timber  shop.  Some  of  the  mines  have  their  own 
sawmills,  and  buy  their  timbers  in  long  lengths  from  the  Port, 
and  cut  all  timbers  to  templates.  They  are  sent  underground 
ready  for  the  miners  and  timberman  to  frame  up  in  the  stopes. 
When  the  ore  is  hard  and  compact  (and  it  is  hard  sometimes, 
especially  in  the  class  of  ore  containing  rhodonite),  I  have  fre- 
quently seen  five  drills  blunted  to  bore  a  hole  less  than  1  in.; 
but  when  the  ore  is  friable,  it  is  then  timbered  close  up  to  the 
working  face  (as  shown  in  Fig.  93)  on  the  upper  floors.  In  this 
system  the  miners  are  always  working  close  to  the  face  or  back, 
which  they  can  easily  examine  to  make  sure  of  its  safety.  One 
disadvantage -of  keeping  the  timbers  so  close  to  the  face  is  that 
frequently  a  heavy  shot  will  'throw, '  and  thus  knock  down 
several  sets  and  shake  others,  thereby  causing  delay  and  render- 
ing the  working  face  unsafe  until  the  timbers  are  re-erected, 
and  there  is  always  difficulty  in  securing  them  all  as  firmly  as  they 
were  originally.  Lagging  of  10  X  2-in.  Oregon  pine  are  laid 
on  each  floor  as  the  stopes  rise  upward  to  the  next  level,  and  chutes 
for  conveying  the  broken  ore  to  the  sills  and  thence  to  the  trucks 
are  provided  at  convenient  intervals,  and  slides  placed  to  run  the 
ore  to  the  chutes  from  the  working  face,  as  shown  on  the  plan 
and  section  showing  the  stope  (Fig.  93).  It  will  also  be  noticed 
that  the  end  sets  of  each  floor  are  wedged  firmly  to  the  foot  and 
hanging  walls  of  the  ore  body,  and  frequently  notches  or  hitches 
cut  to  secure  a  solid  bed.  In  theory,  as  a  system  by  itself,  these 
seem  admirable,  but  in  practice  (without  being  filled  with  waste 


MINING  AT  BROKEN  HILL 


215 


Vertical  Projection 


Horizontal  Section  A-B 

FIG.  93 


216  TIMBERING  AND  MINING 

as  they  now  are)  they  fail,  for  after  the  ore  has  been  extracted, 
any  movement  or  pressure  of  the  walls  of  the  lode  causes  a  collapse 
of  the  set.  They  have  gained  the  weird  name  of  'creeps/  and  a 
more  complete  state  of  chaos  can  hardly  be  imagined  than  a 
creep,  that  is,  broken  and  splintered  timbers,  and  masses  of  ore 
and  mullock  in  one  almost  unapproachable  mass,  often  rendering 
the  further  working  of  that  portion  of  the  lode  impossible,  and 
thereby  losing  large  quantities  of  ore  in  the  debris;  but  it  is  a 
noticeable  fact  that  in  those  mines  where  the  managers  did  not 
rely  on  the  timbers  alone,  but  judiciously  filled  in  the  sets  with 
mullock  from  wall  to  wall  (leaving  only  the  necessary  openings 
for  chutes,  gangways,  etc.),  when  any  movement  came  in  the 
walls  of  the  lode  the  timbers  and  surrounding  filling  stood  the 
burden,  and  the  mines  were  singularly  free  from  'creeps.'  Some 
idea  of  the  pressure  on  these  timbers  may  be  imagined  when  I 
state  that  I  have  seen  a  piece  of  10  X  10  in.  Oregon  pine  com- 
pressed to  barely  3  in.;  have  also  seen  a  10  X  10-in.  vertical  leg 
driven  4£  in.  into  the  horizontal  cap  and  sill  at  its  ends,  without 
bending  the  leg,  and  have  frequently  noticed,  when  there  has  been 
any  lateral  pressure,  the  10-in.  piece  of  Oregon  splintered  like 
a  piece  of  willow  on  the  convex  side,  and  on  the  concave  side, 
though  bent  one  foot,  was  still  unbroken. 

"The  life  of  timbers  underground  depends  a  great  deal  on 
location.  In  some  mines  I  have  noticed  Oregon  pine  that  had 
been  in  approximately  ten  years  almost  sound,  while  in  others 
the  same  class  of  timbers,  if  put  in  a  badly  ventilated  stope,  in 
about  three  or  four  years  had  completely  decayed  by  a  kind  of 
moldy  dry-rot.  In  the  upper  portions  of  one  mine  I  noticed  a 
lot  of  joggled  logs  of  blue  gum,  from  6  in.  to  9  in.  diameter  (brought 
from  the  river  in  early  days) ,  and  they  were  worm-eaten  and  quite 
rotten,  while  the  mulga  and  black  oak,  both  hard  native  timbers, 
were  quite  sound;  but  as  these  latter  are  usually  only  about 
4  in.  to  8  in.  in  diameter,  they  are  almost  useless  for  underground 
timbering,  except  as  lathes,  or  for  latticing  the  sides  of  square- 
sets  and  enclosing  the  mullock  fillings,  for  which  they  are  some- 
times used.  I  omitted  to  mention,  when  describing  the  mullock 
filling  of  the  square-sets,  that  10  X  2-in.  planks  are  used  by  some 
mines,  but  other  mines,  having  their  own  sawmills,  rip  the  10  X 
2-in.  lath  in  halves  and  use  the  5  X  2-in.  lath,  thus  effecting  a 
small  saving  in  the  amount  of  timber  used;  but  I  have  noticed 


MINING  AT  BROKEN  HILL  217 

also  that  these  lighter  laths  frequently  give  way  when  any  great 
pressure  from  the  mullock  is  thrown  on  them.  Other  great  de- 
tractions to  the  square-set  system  are  the  great  cost  of  timber 
and  the  liability  to  fires. 

"  When  considering  the  amount  of  timber  required  to  timber 
a  lode,  the  total  feet  is  enormous,  and  at,  approximately,  $38 
per  1000  ft.,  the  cost  greatly  reduces  the  profits.  We  have  in 
the  Central  a  width  of  over  270  ft.  from  foot-wall  to  hanging-wall 
at  the  600-ft.  level,  the  greatest  width  on  the  Barrier,  taken  out 
in  blocks  about  50  ft.  wide  right  across  from  one  level  to  another, 
viz.,  100  ft.  vertically.  There  is  the  liability  to  fires,  of  which 
the  fire  in  Block  11,  of  about  seven  years  ago,  and  the  fire  in 
Block  12,  of  four  years  ago,  both  of  which  are  still  burning,  are  ex- 
amples. These  cause  great  expense  in  extinguishing,  and  greatly 
hamper  the  working  of  the  upper  portions  of  the  lode.  So  much 
timber  of  inflammable  nature  is  a  great  menace,  especially  when 
the  stopes  are  well  ventilated  by  winzes  from  the  upper  workings. 
These  winzes  serve  as  vents  or  chimneys,  and  spread  the  gases 
throughout  the  mine,  and  the  result  is  loss  of  life,  as  it  was  on 
both  occasions  referred  to,  when  men  went  below  to  locate 
and  attempt  to  overcome  the  fire.  It  will  be  seen  that  the 
deduction  to  be  drawn  is  that  this  system  is  an  admirable 
one  when  combined  with  filling;  but  it  is  also  an  expensive 
one. 

"  Owing  to  the  sulphide  ore  requiring  more  costly  and  tedious 
treatment  and  preparation  before  smelting  than  oxidized  ores, 
and  the  many  and  varied  expenses  incidental  to  the  mining, 
due  to  the  hardness  and  the  work  of  extraction  and  handling,  it 
was  necessary  that  managers  and  others  interested  should  devise 
some  safer  and  cheaper  methods,  which  would  also  reduce  expense. 
Later  methods  have  gradually  evolved  into  their  present  forms; 
and  their  almost  universal  adoption  on  several  mines  on  the  line 
of  lode  —  with  sundry  modification  to  suit  individual  cases  - 
proves  their  efficiency.  The  square-set  system  is  far  from  anni- 
hilated, as  it  is  still  used  where  applicable,  especially  on  the  sill 
floors  where  gangways  are  required;  also  chutes,  outlets,  etc. 
Here  the  sets  are  on  solid  bottoms;  being  well  wedged  against 
the  hanging  and  foot-walls  or  the  sides  of  the  stopes,  they  are 
firm  and  permanent,  and  with  the  10  X  3-in.  planking  to  carry 
the  mullock  filling,  they  form  convenient  passages  about  the 


218  TIMBERING  AND  MINING 

workings.     So   it  is   still   used   in   conjunction  with  these  later 
systems,  as  a  valuable  and  necessary  adjunct." 

Underground  Open-Cut  and  Sloping-Stope  Systems,  at  Broken  Hill 

"The  term  underground  open-cut  system  may  at  first  seem 
erroneous  or  misleading,  as  the  term  open  cut  is  generally  applied 
to  excavations  from  the  surface  downward;  but  the  above  name 
is  that  generally  given  by  the  miners  to  the  large  stopes  which 
are  worked  under  this  system.  The  drives  are  first  run  along 
the  foot  and  hanging  walls,  and  then  through  the  ore  body. 
From  the  upper  levels  winzes  are  sunk  and  cross-cuts  driven  at 
convenient  intervals.  The  winzes  serve  several  important  pur- 
poses. They  ensure  a  complete  and  lasting  ventilation  to  the 
stopes  during  their  upward  way  by  carrying  off  all  noxious  gases 
as  they  form  in  the  lower  workings  or  are  given  off  by  the  sul- 
phide ore,  thus  enabling  the  miners  to  work  with  a  greater  degree 
of  comfort  and  also  to  do  a  fair  shift's  work,  which  could  hardly 
be  expected  in  a  hot  stope  with  a  constant  atmosphere  of  about 
90°.  The  winzes  serve  as  passes  or  chutes  through  which  the 
filling  is  conveyed  from  the  upper  levels,  and,  by  a  succession  of 
chutes  and  winzes  from  the  surface,  deposited  where  desired. 
This  system  is  successful  in  the  Central  mine,  for  the  mullock 
or  waste  is  broken  in  a  large  open  cut  on  the  surface  and  is  con- 
veyed in  side-tipping  trucks,  of  a  capacity  of  one  cubic  yard, 
drawn  by  horses  through  a  tunnel,  then  discharged  into  a  chute, 
from  which,  by  a  series  of  winzes,  chutes  etc.,  it  is  distributed 
throughout  the  mine  where  required.  The  winze  is  used  as  a 
starting  place  or  face  from  which  to  work  the  stope,  and,  after 
the  ore  is  extracted,  say,  the  first  10  or  20  ft.,  it  is  timbered  up 
closely  into  two  compartments,  as  shown  in  Fig.  94.  One  com- 
partment serves  as  a  chute  or  pass  for  the  ore  to  the  sill  floor,  as 
the  stope  works  upwards,  and  the  other  compartment  as  a  ladder 
way  and  means  of  ingress  and  exit  for  the  miners  and  others  to 
the  upper  workings  of  the  stope.  The  sides  of  the  initial  drives 
on  the  sill  floor  are  extended  to  the  desired  width  along  the  lode, 
and  thus  the  stope  is  formed  on  the  sill  floor,  the  sill  timbers 
placed  in  position  and  then  filled  up.  On  top  of  these  timbers 
the  bedding  for  the  filling  is  placed,  as  shown  in  the  section, 
Fig.  95,  being  10  X  10  in.  and  10  X  3  in.  timbers,  arranged  to 
carry  the  burden.  Above  these  'sollars/  as  they  are  called,  the 


MINING  AT  BROKEN  HILL 


219 


only  timbering  is  that  of  the  chute  and  ladder  way,  all  other  spaces 
being  filled  in  with  mullock  from  wall  to  wall,  as  indicated,  which 
is  placed  in  layers  of  7  to  12  ft.  As  the  broken  ore  falls,  and  the 
traffic  also  is  all  on  the  mullock  filling,  each  succeeding  layer 
gets  well  rammed  and  solidifies  before  the  next  one  is  placed  on 
it.  In  the  large  open  stopes  in  the  Central  mine,  almost  all  the 
boring  is  done  by  machine  drills  driven  by  compressed  air.  These 


Longitudinal  Section 

FIG.  94.  —  The  Underground  Open-Cut  System 

bring  down  the  ore  in  large  pieces,  frequently  from  7  to  8  ft.  by 
about  2  ft.  wide.  These  pieces  are  then  bored  by  hammer  and 
drill,  and  popped  into  smaller  sizes,  then  sprawled  into  sizes  — 
generally  less  than  1  ft.  long  —  for  throwing  down  the  chutes 
and  removal  in  the  trucks,  which  are  all  end-tipping  and  hold 
about  1600  Ib.  of  broken  ore.  When  the  'back7  or  top  portion 
of  the  stope  is  'heavy,'  or  seems  dangerous  and  likely  to  come 
away,  bulkheads  are  built  under  it.  These  consist  of  10  X  10-in. 


220 


TIMBERING  AND   MINING 


timbers  placed  at  right  angles  to  each  other,  one  above  the  other 
and  tightly  wedged.  (See  Fig.  94.)  When  bulkheads  are  built 
on  the  mullock  filling,  a  bed  of  10  X  4-in.  sollars  is  first  laid  on  the 
mullock,  to  distribute  the  pressure  over  as  large  area  as  possible; 
then  the  first  10  X  10-in.  timbers  forming  the  bulkhead  are  laid 


End  of  Cap 


Scale  of  Feet 
2 


Plan  showing  Bottom  of  Cap 

FIG.  95.  —  Cross-Section  of  Underground  Open-Cut  System 

transversely  across  the  sollars.  These  timbers  are  afterwards 
removed,  the  burden  shot  down,  and  the  same  timbers  used  over 
and  over  again. 

"  A  somewhat  similar  modification  of  the  same  system,  called 
the  '  sloping-stope  system/  is  shown  in  Figs.  97,  98,  and  99. 
This  method  is  extensively  used  on  the  Broken  Hill  Proprietary 


MINING  AT  BROKEN  HILL 


221 


Wall 


Filled  as  shown  in  Section 


Pi 

«  a 

<  °    Plan  with  Long  Cap  removed 

ft  

rO.                                            A 

OJ. 

Ladder  FE 

5 

ea           x 

!  !  ! 

X 

TT, 

A 

: 

1 

: 

•1 
1 

1 
1 
1 
1 

1 

~4 

TJ_ 
1 

1 
1 

jf 

} 
") 

3 

Plan  with  10 

O"  Stringer  off 

10 
L 

aj 

w                   w                   w 

'IT' 

FIG.  96 


iff     -vS*,- •  -  -  >-C    -•--/'',         I'1/     '. 

K^-V ^-F.illra'g  :^ >}(      '^  l\\  J 


Section"  o'f  Stope  in       Section  of  Stope  Com- 
Course  of  Work.  pleted  and  partially 

Filled. 


Long  Sollars  at  ends  of 
Stringers  let  into  Hitches 


Transverse  Section 


Sloping  in  Horizontal  Layers. 
Adopted  in  Hard  Ground. 


f 

Transverse  Section 

FIG.  97 


Longitudinal  Section 

FIG.  98 


222 


TIMBERING  AND   MINING 


mine,  and  I  am  indebted  to  E.  J.  Harwood,  C.E.,  mining  manager, 
for  permission  to  copy  his  drawings  showing  this  system.  In 
many  instances  the  same  description  will  apply  as  in  the  foregoing 
notes  on  underground  open-cut  stoping,  viz.,  the  levels  on  the 
sill  floors  are  first  formed,  taking  notice  that  the  width  of  the  stope 
depends  on  the  nature  of  the  ore  to  be  mined,  or  its  ability  to 
support  itself  by  leaving  the  back  in  the  form  of  an  arch;  the  whole 
stope,  when  formed,  is  somewhat  in  shape  like  an  isosceles  tri- 
angle, of  which  the  level  or  sill  floor  forms  the  base  and  the  winze 
the  apex;  also,  the  winze,  as  before,  is  sunk  from  the  level  above, 
and  the  stope  is  started,  from  the  winze,  as  in  the  other  open-cut 
system,  while  the  winze  serves  the  same  purpose,  for  ventilating 
and  as  a  pass  for  the  mullock  filling  into  the  stope,  also  as  a  chute 


Blocked 
5"i  2"Uanging  Battens 


FIG.  99.  —  Vertical  Section  of  Stope,  Square-set  System 

for  the  ore  to  the  sill  floor.  The  great  difference  is  that  the  stope 
slopes  laterally  to  each  side,  instead  of  going  up  with  a  level  or 
even  floor,  and  as  these  sides  rise  with  the  stope,  provision  must 
be  made  for  preventing  the  mullock  filling  from  running  into  the 
adjoining  stope  when  it  rises.  This  is  done  by  placing  vertically 
at  the  sides  of  the  stope,  about  5  ft.  apart,  10  X  4-in.  stringers 
which  overlap  at  the  ends,  and  are  then  covered  with  10  X  2-in. 
planks  placed  horizontally  against  the  face  of  the  ore.  These 
may  be  removed  and  used  over  and  over  again.  When  the 
adjoining  stope  is  afterward  being  worked,  the  stoping  advances 
forward  from  5  to  8  ft.  at  a  time,  and  from  8  to  12  ft.  upwards. 
The  advantage  of  these  sloping  sides  is  that  the  broken  ore  falls 
on  10  X  4  in.  sollar  boards  placed  on  the  incline  plane  of  the  mul- 


MINING  AT  BROKEN  HILL  223 

lock,  and  thus  rolls  to  the  chutes  at  the  sides  without  further 
handling,  excepting,  of  course,  the  large  pieces,  which  require 
hand  boring,  popping  and  spawling,  as  before  mentioned.  It 
will  be  noticed  on  referring  to  Fig.  97  that  the  stope  is  filled  in 
with  mullock  to  within  2  or  3  ft.  of  the  back,  and  the  stope  is 
always  worked  downward,  starting  from  the  winze;  10  X  10  in. 
legs  rest  on  the  sollars  (or  on  bed  logs  left  in  the  mullock),  or  at 
right  angles  to  the  sollars  and  also  to  the  back,  as  they  are  nearly 
parallel;  these  are  tightly  wedged  and  blocked  and  only  removed 
as  the  ground  is  taken  out.  When  the  stope  is  about  9  ft.  high, 
the  sollars  are  taken  up  and  stored  aside  for  further  use.  The 
stope  is  mullocked  up  again  to  within  2  or  3  ft.  of  the  back,  when 
the  chutes  are  again  built  up  a  porportional  height  and  the  sollars 
replaced  on  the  mullock,  the  sloping  process,  as  before,  taking 
another  slice  from  the  back,  also  starting  from  the  winze  down- 
ward. The  Broken  Hill  Proprietary  Company  has  of  late  years 
been  adopting  a  modification  of  the  square-set  system  in  working 
these  'sloping  ores'  by  timbering  up  the  middle  of  the  stopes 
with  square-sets,  which  are  filled  with  mullock  as  the  work  pro- 
ceeds; but  as  the  back  —  or  working  face  in  this  instance — is 
sloping,  as  in  the  last  mentioned  method,  each  successive  floor 
of  sets  stands  back  one,  or  in  such  a  manner  that  the  outside 
faces  of  the  sets  follow  as  nearly  as  possible  the  same  angle  of 
inclination  or  inclined  plane  as  the  face  of  the  ore  body.  In  this 
way  the  miners  are  always  within  a  safe  distance  in  working  and 
examining  the  face  and  back  of  the  workings,  and  all  the  favor- 
able points  of  the  other  adaptation  of  the  sloping-stope  system 
apply  to  this  system,  with  the  advantage  that  the  miners  have  a 
good  footing  on  the  set  timbers,  and  the  great  convenience  offered 
for  the  despatch  of  the  ore  through  the  chutes  constructed  in  the 
square-sets." 

Another  modification  o*f  the  square-set  system  as  adopted 
in  the  Central  mine  is  known  as  the  "  block  system  "  (see  Figs.  100 
and  101).  The  lode  for  its  entire  length  through  M.  L.  No.  9  has 
been  surveyed  into  parallel  blocks  each  50  ft.  wide — i.e.,  ten 
5  ft.  wide  sets.  Each  alternate  division  is  a  block  and  the  next  a 
stope.  The  whole  level  is  gradually  developed  by  a  drive  along 
the  foot-wall  and  by  cross-cuts  to  the  hanging-wall,  thereby 
determining  the  width  of  the  lode  along  its  entire  length,  and  the 
stopes  are  then  carried  from  the  foot-wall  to  the  hanging-wall 


224 


TIMBERING  AND   MINING 


on  the  sill  floor  and  the  space  filled  with  square-sets,  leaving 
every  facility  for  forming  the  necessary  gangways,  chutes,  etc. 


Section    B 


Block 


FIG.  100.  —  The  Block  System  of  Stoping.     (Vertical  Section) 


FIG.  101.  —  The  Block  System  of  Stoping  (Horizontal  Section) 

These  are  then  filled  in  with  mullock,  and  the  stope  starts  on  its 
course  upward,  being  exactly  50  ft.  wide,  the  entire  width  of  the 
lode  at  that  point,  thus  leaving  a  pillar  of  ore  50  ft.  wide  in  each 


MINING  AT  BROKEN  HILL  225 

side  of  it  from  wall  to  wall,  which  will  carry  all  pressure  during 
the  mining  of  this  stope.  A  run  of  square-sets  is  put  in  each  side 
of  the  stope  as  it  goes  upward,  forming  a  gangway  and  ladder  way, 
the  sides  of  which  are  lathed  or  paddocked  off,  thereby  confining 
the  mullock  filling  in  the  center  of  the  stope.  The  ore  is  broken 
by  machine  drills  driven  by  compressed  air,  and  in  the  same 
lifts  and  proportions  as  in  the  before-mentioned  open-stope 
system.  The  ore  falling  on  the  mullock  filling  in  the  center  of 
the  stope  is  popped  and  spawled  into  suitable  size  for  handling 
and  trucking  to  the  shaft  for  haulage  to  the  surface.  One  great 
difference  in  this  system  is  that  the  winzes  —  6X5  ft.  —  are 
always  sunk  100  ft.  apart  at  the  side  of  each  alternate  stope, 
being  half  in  the  stope  and  half  in  the  adjoining  block,  thereby 
saving  a  second  winze  when  the  block  is  being  taken  out  at  any 
future  time.  The  ore  from  the  adjoining  stopes  having  been  all 
extracted,  and  the  space  filled  with  the  mullock,  this  winze  will 
then  be  available  and  serve  the  same  purpose  for  the  remaining 
block.  The  same  advantages  of  ventilation,  mullocking  and 
stoping  all  apply  to  these  stopes,  as  in  the  foregoing  open-cut 
and  sloping-stope  systems,  and  they  are  mullocked  up  in  the 
same  manner,  excepting  that  the  chutes  for  conveying  the  ore 
from  the  working  faces  to  the  sill  floor  are  located  in  the  runs 
of  sets,  placed  on  the  side  of  the  stopes  for  that  purpose,  and 
the  chutes  can  be  constructed  at  suitable  intervals  for  the 
workings. 

The  advantages  and  disadvantages  of  these  several  systems 
are:  The  whole  of  the  ore  body  is,  or  at  least  can  be  eventually, 
extracted,  and  after  extraction  of  lode  material  comparatively 
few  if  any  large  voids  or  openings  are  left;  which  also  leaves  the 
surface  areas  for  works,  mill,  machinery,  etc.,  almost  free  from 
risk  of  subsidence.  The  great  advantage  evident  from  the  pres- 
ence of  mullock  filling  —  in  lieu  of  a  forest  of  timber  —  is  the 
immunity  from  risk  of  fire.  The  miner  is  always  in  reach  of  the 
"back,"  i.e.,  from  3  ft.  to  9  ft.,  and  can  readily  sound  and  examine 
the  back  of  the  workings  and  make  sure  they  are  safe;  this  secures 
a  greater  freedom  from  accident  through  masses  of  ore  falling 
on  men  while  at  work  immediately  under  them.  Unfortunately, 
^however,  recent  experiences  have  shown  that  though  a  place 
may  be  sounded  and  examined  by  miners  with  a  lifetime  experi- 
ence and  reported  as  safe,  yet  a  few  hours  afterward  the  back 


226  TIMBERING  AND   MINING 

may  fall  in  and  reveal  a  fault  or  crack  which  the  sounding  did 
not  make  known,  serious  or  fatal  accidents  resulting.  But  even 
then  this  cannot  in  any  way  be  compared  to  the  great  risk  incurred 
by  men  when  re-erecting  square-sets  that  have  been  knocked 
down  by  a  heavy  shot,  for  sometimes  a  charge  will  bring  away 
more  ground  than  anticipated,  and  a  dozen  or  more  sets  will 
come  down,  and  the  men  will  have  to  work  under  a  probably 
dangerous  back  in  re-erecting  the  sets  or  staging  before  they  can 
actually  examine  it  and  assure  themselves  of  its  safety. 

Another  advantage  is  the  saving  in  the  expense  of  timber. 
Of  course,  against  this  must  be  placed  the  cost  of  quarrying  the 
mullock  filling  on  the  surface  and  conveying  it  to  the  stopes, 
which  would,  however,  be  required  in  any  case  in  filling  the  square- 
sets  in  the  other  systems.  The  great  advantage  of  good  air  is 
important,  as  the  mullock  fills  in  all  spaces  except  the  winzes  and 
that  part  of  the  stope  that  is  being  worked,  thus  ensuring  always 
at  the  working  face  a  current  of  air,  which  both  carries  off  the 
smoke  after  firing  and  adds  to  the  miner's  health  and  comfort, 
removing  much  that  in  former  days  made  the  miner's  life  a  hazard- 
ous and  unhealthy  one. 

There  is  one  other  important  method  employed,  by  which  a 
large  amount  of  oxidized  ore  has  been  removed.  I  refer  to  the 
open-cut  system.  The  large  surface  excavations  are  one  of  the 
chief  sights  of  Broken  Hill,  and  though  descriptions  may  give 
a  slight  idea  of  their  extent,  I  think  they  must  be  seen  to  be 
understood  or  appreciated.  Imagine  an  open  cavern,  three- 
quarters  of  a  mile  long,  traversing  the  whole  of  the  Broken  Hill 
Proprietary  Company's  blocks.  The  widths  of  these  cuttings 
vary  from  120  ft.  to  about  350  ft.  There  is  also  a  width  of  300  ft. 
opposite  McGregor's  shaft,  in  the  center  of  Block  11.  The  cuts 
are  down  about  250  ft.,  and  they  are  recovering  a  large  amount 
of  timber  that  was  used  underground  in  the  square-set  system  of 
stoping  in  the  old  200-level  workings,  the  ore  from  which  was  then 
hauled  up  the  various  shafts  before  the  open  cuts  reached  their 
present  depths. 

A  method  by  which  the  greater  part  of  the  ore  is  raised  from 
the  open  cuts  to  the  surface  is  by  means  of  what  is  here  called 
the  "Flying  Fox"  —a  large  skip  which  is  hauled  up  along  an 
aerial  ropeway  and  thence  discharged  into  large  ore  bins  at  the 
sides  of  the  railroad  lines  on  the  surface,  from  which  it  is  con- 


MINING  AT  BROKEN  HILL 


227 


veyed  to  the  mill  or  to  the  smelters.  A  mast  is  erected  on  each 
side  of  the  cut  and  a  cable  stretched  over  an  iron  saddle  near  the 
top.  The  cable  is  anchored  securely  at  either  end,  while  on  the 
surface  is  located  the  hauling  engines,  having  a  loose  pulley  and 
reversing  gear.  An  attachment  called  a  bicycle  runs  along  the 
main  cable  across  the  cut,  having  on  it  four  pulleys.  The  upper 
two  travel  along  the  cable,  the  lower  two  being  used  in  hoisting 
the  skip  vertically  from  the  cut;  the  rope,  called  the  traveling 
rope,  then  draws  the  bicycle,  and,  of  course,  the  skip  with  it, 
along  the  cable.  When  it  is  over  the  bin  on  the  surface  a  self- 
standard  Drive  Timbering. 


acting  catch  holds  it  steady,  while  it  is  lowered  and  discharges 
into  the  bin.  The  skip  is  again  hoisted  and  run  out  along  the 
cable  and  again  lowered  into  the  cut.  In  the  meantime  a  second 
skip  has  been  filled,  and  is  attached,  hoisted  and  discharged  as 
described. 

The  skips  are  about  16  in.  deep,  4  ft.  wide  and  5  ft.  long. 
They  are  suspended  by  four  chains,  one  at  each  corner,  the  back 
two  being  fixed  to  the  skip,  while  the  front  ones  are  fastened  by 
hooks,  which  are  undone  to  release  the  load.  The  skips  are  used 
for  many  purposes.  I  have  seen  a  workman  with  a  broken  leg 
hauled  to  the  surface  and  deposited  safely,  thus  saving  a  climb 
up  the  banks.  The  sides  of  the  cut  are  made  with  a  slope  of  one- 


228  TIMBERING   AND  MINING 

half  to  one  and  three-quarters  to  one,  and  would  meet  at  a  depth 
of  250  ft.;  but  owing  to  the  frequent  slips  of  the  sides  they  are 
often  irregular.  Some  very  heavy  blasting  is  done  in  these  cuts, 
which  shakes  the  ground  for  a  great  distance,  but  great  masses 
of  ore  are  removed. 

The  sets  as  used  in  the  double-track  drives,  where  horses  are 
used  underground,  are  framed  as  shown  in  Fig.  102.  They  are 
designed  to  withstand  heavy  pressure,  and  are  placed  at  intervals 
varying  with  the  nature  of  the  ground  they  have  to  hold,  but 
are  generally  4  ft.  to  5  ft.  between  centers. 


CHAPTER  XXV 

MINING     AT     THE     HOMESTAKE,     LEAD,     SOUTH 

DAKOTA 

THE  Homestake  mine  is  without  exception  the  largest  gold 
mine  in  the  world.  The  great  property  is  operated  through  six 
shafts,  though  a  large  amount  of  ore  is  still  mined  in  open  cuts 
by  the  usual  methods,  the  broken  ore  passing  downward  through 
mill-holes  to  chutes  on  levels  below,  where  it  is  drawn  out  into 
cars,  trammed  to  one  of  the  shafts,  and  hoisted  to  the  surface. 
Until  recently  all  hoisting  was  done  by  means  of  cages,  but  lately 
skips  have  been  introduced  at  some  of  the  shafts.  With  the 
exception  of  the  Ellison  shaft,  all  of  the  several  shafts  of  the 
Homestake  property  are  of  the  usual  rectangular,  3-compart- 
ment  type.  The  Ellison  shaft,  however,  differs  materially  from 
the  others  in  its  dimensions,  having  two  hoisting  compartments, 
each  5  X  10  ft.,  and  a  pump  and  manway  compartment  6  X  10  ft. 
clear.  Figs.  103  and  104  show  the  method  of  timbering  in  this 
shaft.  Timbers  were  loaded  on  flat  cars,  run  on  to  the  cages  and 
lowered  to  the  level  where  they  were  required.  This  saved  much 
time  in  handling  timbers  and  was  found  superior  to  the  usual 
method  of  standing  them  on  end  and  lashing  them  to  the  cage 
frame. 

The  stations  at  the  shafts  of  the  Homestake  were  all  of  liberal 
size,  and  were  cut  from  12  to  16  ft.  high.  Iron  plates  were  laid 
on  the  floors,  so  that  cars  could  be  shifted  about  anywhere 
between  the  track  ends  and  the  shaft,  but  the  sheets  were  later 
taken  up  and  the  rails  were  carried  directly  up  to  the  shaft, 
opposite  each  hoisting  compartment.  The  tracks  in  the  stations 
were  laid  with  turnouts,  so  that  cars  could  be  sent  from  both 
main  tracks  to  either  cage  in  the  shaft.  Fig.  105  shows  the 
arrangement  of  tracks  at  stations  of  the  Ellison  shaft. 

The  main  drifts  in  this  property  are  generally  of  a  single 
type,  illustrated  by  Fig.  106.  All  the  drifts  are  driven  with 

229 


230 


TIMBERING  AND   MINING 


0       © 


0       © 


Wall  Plate     12"x  12"x  20'0 


© 


FIG.  103.  —  Plan  of  Ellison  Shaft 


1 


JA. 


i,--  • -;• 


TT         TJ 


^ 


FIG.  104.  —  Longitudinal  Vertical  Section  Ellison  Shaft 


MINING  AT  HOMESTAKE,   LEAD,   SOUTH  DAKOTA       231 

machine  drills.  Raises  are  made  for  various  purposes,  ventila- 
tion, ore-storage  bins,  transferring  ore  or  waste  from  one  level 
to  another,  or  to  provide  an  opening  through  which  waste  may  be 
dumped  into  a  finished  stope.  Permanent  raises  for  ventilation, 
ore  bins,  etc.,  are  located  in  the  country  rock  far  enough  away 
from  the  ore  body  to  be  undisturbed  by  mining  operations.  The 


Spring  Switch 


FIG.  105 

purpose  of  the  waste  raise  is  to  provide  a  storage  for  waste  taken 
from  dead  work  when  not  immediately  needed  in  the  stopes,  and 
these  are  so  arranged  that  waste  may  be  drawn  out  or  dumped 
in  at  any  level.  The  main  waste  raises  are  connected  with  the 
surface,  and  the  porphyry,  which  forms  a  cap  overlying  the 
ore-bearing  formation,  is  drawn  through  them  and  used  for  filling. 
Fig.  107  shows  the  arrangement  of  one  of  these  continuous  raises, 


232 


TIMBERING  AND  MINING 


which  may  be  used  for  waste  or  ore.     The  ore  raises  do  not,  as  a 
rule,  connect  with  the  surface. 

On  one  or  several  levels,  if  convenient,  cross-cuts  are  driven 
to  the  point  from  which  it  is  desired  to  make  a  raise,  care  being 
taken  to  have  the  cross-cuts  on  the  different  levels  alternate  on 
each  side  of  a  vertical  plane.  When  the  cross-cut  has  been 
driven  far  enough  beyond  the  position  of  the  raise  to  provide  a 
passing  track  for  empty  cars,  the  drift  is  widened;  four  sets  of 
regular  stope  timbers  are  put  in,  in  the  form  of  a  square,  and  an 


FIG.  106.  —  Cross-Section  of  Drift  Showing  Air  pipe,  Drain  and  Electric 

Light 


ordinary  board  chute  built  in  one  set.     Above 
raise  is  gradually  drawn  in  to  a  6  X  6-ft.  raise, 
the  raise  is  carried  up  in  the  usual  manner, 
raise,  about  5  ft.  apart,  are  used  to  sustain  the 
and  serve  as  a  ladder  way.     The  smaller  size 
used,   and  are  hoisted  and  lowered  by  rope 
raise  on  the  level  below  is  located  about  15  ft. 
other,  and  is  cut  straight  to  the  upper  level. 


these  timbers  the 

From  this  point 

Sprags  across  the 

working  platform 

machine-drills  are 

and  pulley.     The 

to  one  side  or  the 

After  connection 


MINING  AT  HOMESTAKE,   LEAD,   SOUTH   DAKOTA        233 

has  been  made,  an  inclined  by-pass  is  made  to  connect  with  the 
upper  raise  above  the  timbers.  Another  small  inclined  raise 
connects  the  lower  raise  with  the  cross-cut,  at  the  top  of  which 
are  located  the  grizzlies.  The  bars  forming  the  grizzlies  are 
spaced  about  one  foot  in  the  clear  so  that  no  large  rock  can  get 
into  the  raise.  The  successful  operation  of  these  continuous 
raises  depends  in  a  great  measure  upon  the  grizzlies.  The  by- 
pass is  closed  by  a  gate  made  of  steel  plate,  sliding  in  cast-iron 
grooves  fastened  to  upright  timbers,  and  operated  by  rack  and 
pinion.  A  similar  gate  is  used  in  the  main  ore  bins  under  the 


Main  Header 

Plan 


Vertical  Section 

FIG.  107.  —  Continuous  Raise 

crushers.  It  works  easily,  and  can  be  operated  gradually,  which 
prevents  rushes  of  rock.  Similar  arrangements  are  made  on  the 
other  levels.  As  soon  as  one  raise  is  made  it  can  be  put  into  ser- 
vice and  the  raise  from  the  lower  levels  finished  when  needed. 

In  making  an  ore-storage  bin,  the  timber  sets  are  carried  up 
six  or  seven  posts  high.  When  connection  is  made  with  the  level 
above,  the  timbers  are  removed,  with  the  exception  of  the  sill 
floor  in  which  the  chutes  are  located.  The  by-pass  and  small 
raise  to  the  grizzlies  are  located  as  in  the  waste  raise.  Ingersoll 
A-32  machines  are  usually  used  in  making  raises.  One  miner 
and  helper  will  make  a  6  X  6-ft.  raise  100  ft.  high  in  ordinary 


234 


TIMBERING  AND   MINING 


ground  in  sixty  shifts;  provided  they  are  not  required  to  tram 
the  rock.  Blasts  are  fired  by  ordinary  caps  and  fuse.  When  a 
stope  has  been  worked  nine  or  ten  floors  high,  raises  are  put  up 
in  convenient  places  to  the  level  above,  through  which  the  filling 
is  dumped.  These  raises  are  all  in  ore,  and  consequently  pay 
their  own  way. 

When  a  raise  is  to  be  made  near  the  face  of  a  long  tunnel 
where  the  air  is  bad,  some  artificial  means  of  ventilation  must 


2-2J$"xl()"x2'=i 

2-  2J<"x  I0"x  3'4"=14'l 

1-  4"x  I0"x  3'lO'=13'B« 
6- 9 'Lagging 
l-7'6"Ugging 

2- 4'6 "Lagging 
2-5'Lagging 

2-  2 '6  Lagging 
6^  Lba.  GOd  Nails 
2  Lbe.  40d  Nails 

6-  68  Lb».  %"Drift  Pins 

FIG.  108 

be  provided.  A  device  introduced  here  has  proven  successful. 
A  6  or  8  in.  light  iron  pipe  is  laid  from  the  entrance  of  the  drift 
to  the  foot  of  the  raise.  Near  the  entrance  a  small  £-in.  pipe 
is  tapped  into  the  main  air  pipe  and  brought  down  to  and  into 
the  large  pipe,  with  the  end  which  projects  into  the  pipe  turned 
out.  It  has  been  found  that  a  small  amount  of  air  under  a  pres- 
sure of  from  75  to  80  Ib.  will  effectually  clear  the  raise  in  a  few 
minutes.  This  device  is  used  also  in  running  long  drifts.  An 
exhaust  fan  would  possibly  be  a  more  economical  machine  so  far 


MINING  AT  HOMESTAKE,   LEAD,   SOUTH  DAKOTA        235 

as  power  is  concerned,  but  the  first  cost  would  be  greater,  and 
the  air  is  used  only  when  the  machine  drill  is  not  in  service.  All 
chutes  are  of  the  ordinary  type,  with  bottoms  made  of  lagging 
and  sides  of  2-in.  plank.  The  rock  is  held  back  by  two  boards, 
one  higher  than,  but  not  directly  above,  the  other.  Fig.  108 
shows  the  method  of  building  these  chutes. 

The  Homestake  mills,  six  in  number,  contain  1000  heavy 
stamps,  the  duty  of  each  stamp  being  about  4  tons  per  24  hours. 
These  mills  are  now  crushing  annually  over  1,400,000  tons  of 
ore  —  more  than  4,000  tons  daily.  About  80  per  cent,  of  this 
vast  tonnage  is  taken  from  underground  stopes,  the  remainder 
from  the  open  cuts.  The  ore  obtained  from  the  open  cuts  is 
broken  down  from  the  sides  into  openings  that  connect  with  the 
regular  levels  of  the  mine.  These  openings  or  raises  are  provided 
with  chutes  on  the  different  levels,  from  which  the  cars  are  loaded. 
The  loaded  cars  are  made  up  into  trains  of  from  four  to  eight  cars, 
according  to  the  grade  of  track,  and  are  drawn  by  horses  to  a 
central  point  and  long  trains  are  then  hauled  to  the  shaft  by 
compressed  air  motors. 

The  ore  taken  from  open  cuts  is  mined  very  cheaply.  Two 
miners  whose  wages  are  $3.50  per  day  will  break,  on  the  average, 
200  tons  in  one  shift.  Two  men  are  employed  at  the  chutes,  one 
to  break  the  rock  at  the  grizzlies  and  one  to  load  the  car.  The 
grizzlies  are  located  two  or  three  floors  above  the  chute.  Ore 
and  waste  are  blasted  down  together,  and  the  waste  is  sorted  at 
the  chute  and  used  for  filling. 

In  one  of  the  open  cuts  now  being  worked,  the  process  of 
mining  is  much  like  the  work  of  making  a  very  deep  cut  through 
a  hill  some  300  ft.  high.  Tracks  are  laid  from  the  crushers  to 
one  end  of  the  cut,  and  the  rock  is  blasted  down,  loaded  into 
cars,  and  trammed  directly  to  the  crushers.  The  pillars  and  backs 
of  old  stopes  which  were  left  in  place  in  the  older  workings  of 
the  mine  are  removed  by  a  system  of  draw  raises. 

It  is  very  important  to  know  the  exact  location  of  these 
pillars  and  roofs  before  starting  this  system.  If  the  maps  and 
stope  records  have  been  accurately  kept  this  becomes  an  easy 
matter;  otherwise  the  memory  of  some  old  employe  must  be 
depended  upon  to  give  the  necessary  information.  Having 
located  the  ore,  a  nine-post  raise,  which  consists  of  four  regular 
stope  sets  arranged  in  a  square,  is  put  up  either  on  the  foot-wall 


236  TIMBERING  AND   MINING 

or  on  the  hanging-wall  side,  preferably  the  foot-wall.  This 
raise  is  carried  up  a  sufficient  height  to  reach  the  ore  above  the 
waste  filling.  Grizzlies  are  put  in  on  the  floor  next  to  the  top 
and  the  sides  of  the  raise  are  carefully  lagged  to  protect  the  men. 
The  run  of  ore  is  then  started  by  a  blast  or  by  barring.  A  man 
stationed  at  the  grizzly  breaks  the  rock  so  that  it  will  pass  through 
into  the  chute  which  is  located  on  the  sill  floor. 

The  timber  required  to  make  a  nine-post  raise  four  floors 
high  consists  of  36  posts,  24  caps,  24  ties,  about  150  lagging, 
4  slope  ladders,  and  one  ordinary  board  chute.  The  grizzlies 
are  made  by  placing  two  or  three  12-in.  timbers,  spaced  12  in. 
apart,  over  one  set  of  timbers,  and  protecting  these  by  pieces  of 
sheet  iron  curved  to  fit.  The  posts  on  the  top  floor  may  be  pro- 
tected in  a  similar  manner  from  the  blasts  and  from  running 
rocks.  Fig.  108  illustrates  a  nine-post  raise,  and  the  method  of 
working  a  caved  stope. 

Sixteen  thousand  tons  of  ore  were  taken  from  one  raise  in 
six  months;  and  this  was  done  in  a  place  where  vain  attempts 
had  been  made  to  reach  the  ore  by  carrying  up  timbered  stopes 
through  the  old  fill.  Should  the  ore  be  too  solid  to  run,  the  raise 
will  serve  as  a  manway  to.  a  timbered  stope  started  on  the  top  of 
the  fill.  Whenever  a  run  of  waste  is  encountered,  it  is  drawn 
down  and  used  for  filling  in  other  parts  of  the  mine,  and  the  ore 
from  upper  levels  will  follow  the  waste  down. 

In  former  years,  all  stopes  in  the  Homestake  and  Highland 
mines  were  timbered  by  the  square-set  method.  An  enormous 
amount  of  timber  was  required  in  the  excavations,  and  the  work 
of  handling  the  timber  through  the  shafts  made  it  difficult  to 
hoist  sufficient  ore  to  supply  the  stamps.  The  Nevada  square-set 
system  was  employed  wherever  square-sets  were  used  in  these 
mines.  The  system  was  employed  as  soon  as  underground 
mining  began  on  the  lode  in  1878.  No  unusual  features  were 
introduced,  and  as  filling  was  neglected  in  those  early  days, 
numerous  disastrous  caves  occurred  in  nearly  every  large  mine 
on  the  lode.  The  cave  in  the  Caledonia  mine,  one  of  the  group, 
was  a  particularly  interesting  one.  A  cross-cut  adit  over  800  ft. 
in  length  was  run  to  the  main  ore  body,  which  was  over  200  ft. 
wide  measured  horizontally.  A  vertical  shaft  was  sunk  from  the 
adit  level  in  the  center  of  this  mass  of  ore,  reaching  the  foot- 
wall  in  a  depth  of  about  100  ft.  A  pillar  of  ore  30  ft.  square  was 


MINING  AT  HOMESTAKE,   LEAD,   SOUTH   DAKOTA        237 

left  around  the  shaft  when  stoping  began  on  this  level  and  the 
next  below  it,  but  it  was  insufficient,  and  the  great  weight  of  the 


FIG.  109.  —Nine  Post  Raise  to  Work  Back  of  Caved  Stope 

superincumbent  ore  and  hanging  country  caused  the  great  timbers 
of  the  square-set  to  jack-knife,  and  the  upper  workings  —  ma- 


238  TIMBERING  AND  MINING 

chinery,  timbers  and  all  —  plunged  in  a  chaotic  mass  into  the 
stope  below. 

In  the  Homestake  mine,  on  the  upper  levels,  where  the  ledge 
was  broken  and  comparatively  narrow,  the  sill-floor  excavation 
was  made  from  wall  to  wall,  and  sometimes  for  the  entire  length. 
The  sill-floor  timbers  were  then  put  in  and  stopes  worked  where 
convenient.  When  the  ledge  began  to  widen  this  method  proved 
disastrous,  and  thousands  of  feet  of  lumber  were  used  to  make 
bulkheads  in  a  vain  endeavor  to  keep  the  stopes  open.  The  old 
square-set  method  proving  so  unsatisfactory  in  all  of  the  mines 
of  the  lode,  efforts  were  made  to  devise  a  different  system  of  ore 
extraction  —  one  that  would  require  the  employment  of  less 
timber.  The  first  notably  successful  departure  from  the  old 
practice  was  that  in  the  Deadwood-Terra  mine. 

Sloping  without  Timbers  at  the  Homestake 

The  most  important  of  the  mining  methods  evolved  at  the 
Homestake  is  that  of  stoping  with  the  use  of  a  minimum  of 
timbers  or  with  none  at  all.  The  latter  was  carried  on  in  the 
Deadwood-Terra  mine,  now  a  part  of  the  consolidated  Homestake, 
for  a  number  of  years  prior  to  the  time  when  the  Homestake 
Company  assumed  control.  A  cross-cut  from  the  shaft  intersects 
the  ledge,  which  was  opened  from  wall  to  wall  throughout  the 
entire  length.  All  the  ore  was  removed  from  the  sill-floor  exca- 
vation. As  soon  as  the  ore  body  was  sufficiently  developed,  a 
drift  was  driven  in  the  foot-wall,  approximately  parallel  to,  and 
about  20  ft.  from  the  ore,  and  openings  made  from  the  drift 
into  the  ore  chamber  at  convenient  intervals.  The  ore  was  then 
broken  down  and  the  surplus  removed  through  these  openings. 
As  the  miners  used  the  broken  ore  as  a  staging  to  work  on,  until 
the  stope  was  finished  only  about  40  per  cent,  of  the  ore  could  be 
removed.  The  stopes  worked  by  this  method  are  from  30  ft.  to 
50  ft.  wide,  and  the  dip  of  the  ledge  is  75°  above  horizontal. 
Stoping  may  be  carried  on  in  several  levels  at  the  same  time, 
provided  sufficient  back  is  left  in  between  levels.  When  the  level 
above  is  finished,  this  back  may  be  caved,  and  all  the  rock  removed 
on  the  level  below.  No  timber  is  required  other  than  a  few  lagging 
for  staging,  but  the  method  is  not  applicable  to  wide  ledges.  Fig. 
110  shows  a  cross-section  of  several  levels  and  a  part  plan  of  one 
level,  showing  the  method  of  operation.  The  sketch  of  vertical 


MINING   AT  HOMESTAKE,   LEAD,   SOUTH   DAKOTA        239 

section  fails  to  show  the  raises  necessary  for  manway  and  for 
ventilation.      This  is  shown,  however,  in  the  plan. 

A  new  method  was  inaugurated  by  W.  S.  O'Brien  on  the  600-ft. 
level  of  the  Homestake  mine.  The  plan  is  as  follows:  A  cross-cut 
is  driven  through  the  ledge  from  the  central  shaft,  which  is  called 
the  main  cross-cut.  The  ore  body  is  then  developed  by  driving 
a  24-ft.  drift  along  the  foot-wall.  From  this  drift  stopes  60  ft. 
wide  are  opened  across  the  ledge  (500  ft.),  with  60-ft.  pillars 
between  each  stope.  Beginning  with  the  main  cross-cut,  a  pillar 
is  left  on  each  side,  then  a  60-ft.  room,  a  60-ft.  pillar,  and  so  on 


o  Shaft 


To  Shaft 


/To  Shaft 


Vertical  Cross  Section  of  Deadwood  - 
Terra  Stope  System  without  Timbers 


Horizontal  Section 


FIG. 110 


to  the  end  of  the  ore  body.  These  rooms  and  pillars  are  num- 
bered north  and  south  of  the  main  cross-cut.  No.  3  stope  north 
would  be  the  third  stope  north  of  the  cross-cut,  and  No  4  stope 
south  the  fourth  stope  south  of  the  cross-cut.  Some  difficulty 
was  experienced  in  keeping  the  sides  of  the  rooms  straight  while 
the  sill  floor  was  being  opened.  To  overcome  this  sills  were  laid 
in  the  foot-wall  drift  to  lines  given  by  the  surveyor,  and  the 
miners  took  their  lines  from  these.  Each  stope  contains  eleven 
lines  of  sills.  When  the  system  once  became  established,  no 
difficulty  was  experienced  in  keeping  the  room  of  uniform  width 


240  TIMBERING   AND   MINING 

and  the  sides  comparatively  straight.  When  a  stope  has  been 
worked  and  filled,  the  pillar  may  be  attacked,  the  lagging  on 
the  sides  keeping  the  filling  in  place  so  that  all  the  ore  in  the 
pillar  may  be  removed.  In  these  stopes  the  square-set  system  of 
timbering  was  at  first  employed. 

However  satisfactory  this  method  of  blocking  out  the  ore 
body  may  be,  it  did  not  solve  the  timber  problem.  It  was  finally 
decided  to  try  stoping  in  these  rooms  without  timbers.  As  the 
result  of  the  experiments  the  level  is  opened  by  the  room  or 
block  method,  and  sills  are  laid  in  the  rooms  the  same  as  for 
timbered  stopes.  When  the  sills  are  in,  three  lines  of  track  are 
laid,  running  lengthwise  of  the  stope  but  crossing  the  ledge  from 
wall  to  wall,  with  as  many  cross  tracks  connecting  them  as  are 
necessary.  The  sill-floor  sets  are  put  up,  and  lagging  placed 
over  the  top.  The  tracks  are  protected  by  double  lagging  on 
top,  and  the  rock  is  prevented  from  running  in  at  the  sides  on  to 
the  tracks  by  lagging  or  slabs  spiked  to  the  posts. 

As  soon  as  the  timber  is  in  position  stoping  begins.  The  ore 
is  broken  down  and  allowed  to  fall  through  the  lagging,  entirely 
filling  the  sill-floor  sets,  with  the  exception  of  the  car  ways.  The 
lagging,  which  serves  merely  as  a  staging,  is  removed  as  fast  as 
the  sets  are  filled  with  broken  ore.  No  rock  is  removed  from  the 
stope  until  this  filling  is  finished.  When  the  next  cut  or  breast 
is  carried  across  the  back  of  the  stope,  some  ore  must  be  removed 
to  make  room  for  the  miners.  In  the  large  stopes  two  D-24 
Ingersoll  machines  are  employed,  with  from  one  to  two  "baby" 
machines,  which  are  used  to  drill  block-holes  in  larger  slabs  and 
boulders.  For  block-holing  generally,  however,  the  small  pneu- 
matic-hammer drills  are  used  to  great  advantage.  This  machine 
will  quickly  drill  holes  from  6  to  12  in.  deep,  and  has  proven  very 
successful  in  block-holing  large  boulders  in  the  open  stopes. 

As  there  are  no  timbers  to  break,  no  limit  is  placed  on  the 
miner  as  to  the  amount  of  rock  he  may  bring  down  at  one  blast. 
The  stope  should  be  finished  as  quickly  as  possible,  so  that  the 
broken  rock  may  all  be  removed  if  needed.  Consequently,  large 
slabs  of  ore  are  blasted  down,  and  these  must  be  broken  up  to  car 
size,  either  on  top  of  the  pile  or  on  the  sill  floor,  as  it  is  drawn 
down  by  the  shovelers.  On  account  of  the  uneven  size  of  the 
rocks,  chutes  are  not  generally  used  in  these  stopes,  muckers 
shoveling  the  ore  into  cars  from  the  level  of  the  track,  there  being 


MINING   AT  HOMESTAKE,   LEAD,   SOUTH   DAKOTA        241 


ODD 
ODD 
ODD 
GOD 


242 


TIMBERING  AND  MINING 


as  many  places  to  shovel  from  as  there  are  spaces  between  posts 
along  the  tracks.  However,  where  the  rock  is  soft  and  where  it 
breaks  fine,  chutes  are  used  to  advantage.  Should  a  large  rock 
come  down  which  the  shovelers-  cannot  break  with  a  rock 
hammer,  the  car  is  moved  to  another  opening  until  the  "block- 
holer"  comes  around.  Two  or  three  regular  sets  on  each  side  of 
the  stope  are  carried  up  as  fast  as  the  stope  is  worked,  in  which 
are  placed  the  ladders  and  air  pipes.  These  open  sets  also  assist 
in  ventilating  the  stope.  Fig.  Ill  illustrates  the  Homestake 
method  of  stoping  with  the  minimum  of  timbers. 


FIG.  112.  —  Block  System  of  Stoping  at  the  Homestake  with  Minimum  of 

Timbers 

When  the  stope  is  worked  up  80  or  85  ft.,  raises  are  made 
to  the  level  above,  through  which  the  filling  is  to  be  dumped,  and 
the  ore  is  then  drawn  out.  While  the  ore  is  being  drawn  out 
the  walls  and  roofs  are  carefully  watched  and  all  loose  material 
is  dressed  down.  When  one  end  has  been  emptied  of  ore,  a  sec- 
tion of  the  sill  floor  is  lagged  and  the  filling  is  dumped  in  until  it 
begins  to  run  over  the  lagging.  In  this  way  the  filling  follows 
the  shovelers  and  the  walls  of  the  stope  are  supported  at  one  end 
by  the  ore  and  at  the  other  by  the  waste.  When  small  ore  bodies 


MINING  AT  HOMESTAKE,  LEAD,  SOUTH  DAKOTA         243 

are  worked  by  this  method  no  pillars  are  left,  but  when  one  sec- 
tion is  worked  to  a  sufficient  height,  another  section  is  started  at 
one  end  and  the  ore  is  left  in  until  the  entire  body  is  worked. 
As  only  a  small  per  cent,  of  the  ore  can  be  removed  before  the  stope 
is  finished,  there  is  of  necessity  a  large  reserve  always  on  hand, 
which  allows  the  mine  to  lay  off  miners  whenever  desirable. 
The  broken  ore  reserve  in  the  mine  is  over  1,000,000  tons. 

Another  plan  of  working  these  stopes  has  been  evolved  from 
the  experience  gained  by  employment  of  the  method  above 
described,  by  means  of  which  at  least  50  per  cent,  of  the  sill-floor 
timbers  is  saved.  Instead  of  the  two  outside  tracks  being  laid 
in  the  stope,  a  drift  is  cut  under  the  edge  of  each  pillar  of  sufficient 
height  and  width  to  receive  one  line  of  regular  stope  sets,  and 
tracks  are  laid  in  these.  The  timbers  are  put  in  place,  and  the 
ore  is  broken  down  until  the  sill  chamber  is  partly  filled,  the  broken 
rock  holding  the  timber  sets  in  place.  A  drift  is  run  through  the 
broken  rock  in  the  center  of  the  stope,  in  which  another  line  of 
sets  is  put  up.  No  sills  are  laid  between  the  rows,  and  only  six 
rows  of  posts  are  required,  whereas  eleven  rows  are  required  in 
the  other  stopes.  The  tracks  are  laid  in  these  open  sets  and 
the  two  under  the  pillars  may  be  used  again  when  the  pillar  is 
being  taken  out. 

The  operation  of  these  stopes  has  brought  out  another  change 
in  the  general  working  plan  of  the  mine  which  will  make  a  material 
saving  in  the  cost  of  development.  Timbered  stopes  cannot  be 
worked  economically  more  than  80  or  90  ft.  high,  as  the  timber 
begins  to  crush  of  its  own  weight,  while  the  untimbered  stopes 
can  be  carried  up  150  ft.  as  well  as  100  ft.  As  a  result,  the  dis- 
tance between  new  levels  will  be  made  150  ft.,  which  will  effect 
a  saving  of  one-third  in  development  work,  and  one-third  more 
ore  can  be  recovered  from  the  stopes  with  the  same  sill-floor  work. 

Fig.  Ill  illustrates  the  Homestake  methods  of  stoping  with, 
and  Fig.  112  the  method  without,  sill-floor  sets.  That  employ- 
ing the  timber  sets  on  the  sill  floor  is  similar  to  the  method  in 
use  at  Broken  Hill,  New  South  Wales,  described  and  illustrated 
elsewhere. 

Usefulness  of  Mine  Models 

A  good  model  of  the  workings  of  a  mine  is  of  great  value  in 
laying  out  work  and  in  studying  mine  methods.  With  a  properly 


244  TIMBERING  AND  MINING 

constructed  model,  the  superintendent  and  foremen  can  advan- 
tageously study  out  improved  methods  and  note  the  probable 
effect  upon  existing  workings  and  on  those  yet  to  be  made.  There 
is  in  the  office  of  the  Homestake  Company  an  elaborate  model  of 
a  timbered  stope.  The  model  is  about  5  ft.  square  and  has  been 
carefully  made,  showing  every  detail  of  the  work.  Not  a  stick  of 
timber  used  in  actual  practice  is  absent  in  the  model,  and  by  a 
careful  study  of  this  miniature  stope  inportant  changes  in  methods 
have  been  worked  out.  The  management  of  the  Treadwell 
mine,  in  Alaska,  employs  a  model  of  that  property,  made  from 
plaster  of  Paris,  for  similar  and  other  purposes,  the  model  being 
sawed  into  sections.  The  managers  of  other  properties  make  use 
of  mine  models,  and  they  are  always  found  useful,  as  they  make  it 
possible  to  present  the  broader  problems  involved  within  a  space 
immediately  under  the  eye.  Maps,  of  course,  have  similar  advan- 
tages, but  a  properly  constructed  model  is  better  for  the  pur- 
pose of  studying  practical  mining  problems  than  the  best  map. 

The  following  table,  prepared  by  B.  C.  Yates,  engineer  for 
the  Homestake  Company,  shows  the  comparative  cost  of  mining 
with  the  old  square-set  method  and  by  the  later  method,  where 
relatively  little  timber  is  used: 


MINING  AT  HOMESTAKE,  LEAD,  SOUTH  DAKOTA         245 


TIMBERED  STOPE 


NAME  OF  PIECE 

Number  of 
Pieces 

Lineal  Feet  or 
Feet  Board 
Measure 

Cost  of 
Material 

Labor,  Saw- 
ing and 
Framing 

Total 

Sill  -floor  posts    .  . 
Upper-floor  posts 
Caps  .  . 

421 

2,077 
2,410 

3,650 
16,616 
13,255 

$474.50 
2,160.08 
1,723.15 

$96.83 
477.71 
506.10 

$    571.33 
2,637.79 
2,229  25 

Ties 

2261 

12,435 

1,616.55 

474.81 

2  091  36 

Sills  —  203  long, 
382  short  

4,537 

226.85 

22.69 

24954 

Lagging  
Lagging  strips    .  . 
Wedges  

13,020 
2,410 
2,352 

75,906 
4,025 

784 

3,795.30 
64.82 
13.33 

379.53 
30.00 
11.76 

4,174.83 
94.82 
2509 

47  sill-floor  chutes 
—  complete 

311  68 

16  25 

32793 

215     upper-floor 
bins    —    com- 
plete     

786.22 

37.90 

824.12 

Ladders 

14 

117 

1  99 

3.50 

5.49 

Labor        placing 
timbers       and 
chutes 

4.745  00 

Breakage     (10% 
of  lagging,  5% 
posts,  caps  and 
ties 



79397 

Totals 

$11,174.47 

$2,057.08 

$18,770  52 

STOPE  WORKED  BY  HOMESTAKE  METHOD 


Sill  -floor  posts   .  . 

421 

3,650 

474.50 

96.83 

571.33 

Caps  

410 

2,250 

293.15 

86.10 

379.25 

Ties 

381 

2,095 

272.35 

80.01 

352.36 

Sills,  long   

203 

2,436 

121.80 

12.18 

133.98 

Sills,  short    

382 

2,101 

105.05 

10.50 

115.55 

Lagging  

1,752 

10,214 

510.70 

51.07 

561.77 

Lagging   to   pro- 

tect track  

764 

4,454 

222.70 

22.27 

244.97 

Relief  lagging  .  .  . 

1,684 

13,472 

673.60 

67.36 

740.96 

Wedges  

200 

66 

1.12 

1.00 

2.12 

246 


TIMBERING   AND   MINING 
MANWAYS 


Upper-floor  posts 
Caps  .  . 

96 

48 

768 
264 

99.84 
34.32 

22.08 
10.08 

121.92 
44.40 

Ties  
Lagging,  floors  . 
Lagging,  sides    .  . 
"Drift  pins  

48 
96 
720 
1,440 

264 
560 
4,197 
457  Ibs. 

34.32 

28.00 
209.85 
22.85 

10.08 
2.80 
20.98 

44.40 
30.80 
230.83 

22.85 

Ladders  
Labor  standing 
sill  -  floor    tim- 
bers        .... 

28 

235 

4.00 

7.00 

11.00 
758.  16 

Totals   .    .  . 

$3,108.15 

$500.34 

$4,366.65 

Seventy-three  thousand  tons  were  taken  from  this  stope.  $18,770.52  -4- 
73,000  =  $0.257  per  ton  by  former  method;  $4366.65  -*-  73,000  =  $0.060 
per  ton  by  Homestake  method;  $0.257  —  $0.060  =  $0.197  saving  per  ton. 

The  ore  of  the  lower  levels  of  the  Homestake  mine  is  horn- 
blendic  schist  containing  considerable  finely  disseminated  iron 
sulphide.  This  rock  weighs  200  Ib.  per  cubic  foot,  therefore  but 
10  cu.  ft.  (instead  of  13  ft.,  as  usual)  are  required  to  weigh  one 
ton. 


CHAPTER  XXVI 

WORKING  DANGEROUS  GROUND  IN  THE  KIMBERLEY 
DIAMOND   MINES 

ALL  who  are  familiar  with  the  diamond  mines  of  South  Africa 
are  aware  that  in  the  early  years  of  mining  in  that  field  the  mines 
were  worked  as  open  pits,  the  largest  of  which  covered  many 
acres.  The  pits  varied  somewhat  in  depth,  but  in  the  later  years 
were  500  ft.  below  the  rim  at  the  deepest  place.  The  diamond- 
iferous  ground  was  worked  up  to  the  barren  country  rock  which 
surrounded  the  crater,  leaving  the  great  open  cut  with  vertical 
walls.  Rock  caved  from  the  rim  as  the  work  proceeded,  and  as 
the  central  portion  of  the  pit  grew  deeper,  the  frequency  and 
danger  of  caves  of  rim  rock  increased,  thousands  of  tons  falling 
at  a  time,  until  finally  open-pit  mining  was  discontinued  alto- 
gether. 

Vertical  shafts  were  then  sunk  in  the  country  rock  at  a  dis- 
tance of  several  hundred  feet  from  the  edge  of  the  pit.  Levels 
were  driven  from  the  shafts  to  the  diamond-bearing  ground 
some  distance  beneath  the  lowest  portion  of  the  open  pit,  and 
the  ground  removed  by  stoping.  The  removal  of  that  portion 
just  underneath  the  debris  caved  from  the  rim  is  attended  with 
great  danger,  but  a  method  of  recovering  the  ground  has  been 
devised  which  makes  it  fairly  safe. 

Gardner  F.  Williams  thus  describes  the  method  of  mining 
introduced  by  him  at  Kimberley,  in  his  splendid  work,  "The 
Diamond  Mines  of  South  Africa":  "Instead  of  attempting  to 
withstand,  even  for  a  time,  the  pressure  of  the  superincumbent 
mass  of  broken  reef  (this  is  barren  rock  that  fell  into  the  great 
open  pit  from  the  walls  of  the  crater,  thousands  of  tons  of  which 
overlaid  the  diamond-bearing  ground  in  the  huge  chimney  or 
deposit),  the  new  system  introduced  was  a  caving  in  and  a 
filling  of  the  excavations  after  precious  blue  ground  had  been 
extracted.  When  numerous  small  tunnels  had  been  driven  to  the 

247 


248  TIMBERING  AND  MINING 

margin  of  the  mine,  that  is,  to  the  point  where  they  reached  the 
sides  of  the  crater,  the  blue  ground  was  stoped  on  both  sides 
of,  and  above,  each  tunnel  until  a  chamber  was  formed  extending 
along  the  face  of  the  rock  (wall)  for  100  ft.  or  more,  with  an 
average  width  of  20  ft.,  and  about  20  ft.  high.  The  roof  of  the 
chamber  or  gallery  was  then  blasted  down  or  allowed  to  break 
down  by  the  pressure  of  the  overlying  mass  of  broken  diamond- 
bearing  ground  or  (the  barren)  debris. 

"In  the  early  stages  of  underground  mining  there  was  an 
enormous  amount  of  diamond-bearing  ground  which  had  been 
left  behind  when  open  mining  was  discontinued,  and  which  had 
been  crushed  either  by  the  moving  sides  of  the  immense  opening 
or  by  the  collapse  of  the  underground  pillars  when  mined  by  the 
old  system  (of  pillar  and  room).  It  happened  frequently,  after 
breaking  through  to  the  loose  ground  above,  that  clean  diamond- 
bearing  ground  would  run  down  as  fast  as  it  was  removed  for 
weeks  or  months  at  a  time.  The  galleries  would  at  times  become 
blocked  with  large  pieces  of  blue  ground,  which  had  to  be  blasted, 
and  then  a  further  run  of  blue  ground  would  follow.  When  the 
blue  ground  was  worked  back  toward  the  center  of  the  crater, 
larger  boulders  or  fragments  of  basalt  which  had  come  down 
through  the  loose  reef  from  the  surface  would  be  met  with.  This 
system  of  working  would  be  continued  until  reef  alone  came 
down,  the  waste  or  reef  removed  being  sent  to  the  surface  by 
itself  and  piled  on  the  waste  dump.  It  formed  only  an  incon- 
siderable proportion  (one  to  four  per  cent.)  of  the  total  output. 
When  the  roof  caved  in,  the  gallery  was  nearly  full  of  blue  ground. 
Only  a  part  of  this  ground  was  removed  by  the  men  working 
on  that  level,  the  miners  preferring  to  take  it  out  on  the  next 
level  below.  This  process  of  mining  was  repeated  from  level  to 
level  until  finally  there  was  no  more  loose  ground  to  be  recovered. 
The  cost  of  extracting  blue  ground  while  loose  ground  existed  was 
very  low. 

"  Now  all  this  is  changed,  and  the  plan  of  opening  new  levels 
has  altered  somewhat,  but  the  system  remains  the  same.  When 
the  underground  work  had  reached  a  depth  of  800  ft.  or  more,  a 
new  danger  appeared.  The  huge  open  mines  are  filled  with 
debris  from  the  sides,  caused  by  the  removal  of  the  diamond- 
bearing  ground  by  open  quarrying  to  depths  varying  from  200 
to  500  ft.  As  the  supports  were  removed  the  sides  caved  and 


WORKING  DANGEROUS  GROUND 


249 


filled  the  open  mine.     This  debris  was  composed  of  the  surface 
red  soil,  decomposed  basalt,  and  friable  shale,  which  extended 


FIG.  113.  —  Vertical  Section  Kimberley  Diamond  Mine 

from  the  surface  down  to  a  depth  of  about  300  ft.  In  addition 
to  the  debris  from  the  surrounding  rocks,  there  were  huge  masses 
of  'floating  shale/  resembling  indurated  blue  clay  more  than 


250  TIMBERING   AND  MINING 

shale.  Large  heaps  of  yellow  ground  and  tailings,  which  the 
early  diggers  had  deposited  near  the  margin  of  the  mines,  and 
west-end  yellow  ground,  contributed  to  the  mud-making  material. 
The  black  shale  which  surrounds  the  mines  disintegrates  rapidly 
when  it  falls  into  them.  It  contains  a  small  percentage  of  car- 
bonaceous matter,  and  a  large  amount  of  iron  pyrites.  When 
the  huge  masses  of  shale  fell  into  the  open  mine,  they  frequently 
ignited,  either  by  friction  or,  more  probably,  by  spontaneous 
combustion,  as  they  have  been  known  to  do  on  the  dumps,  and 
burned  for  months  and  even  years  at  a  time.  These  masses  of 
burned  shale  become  soft  clay  and  form  a  part  of  the  mixture 
which  fills  the  open  crater.  This  debris  moves  down  as  the  blue 
ground  is  mined  from  beneath  it,  and  becomes  mixed  with  the 
water  which  flows  into  the  open  mine  from  the  surrounding  rock, 
and  with  storm  water,  and  forms  mud.  This  overlying  mud 
becomes  a  menace  to  the  men  working  in  the  levels  below.  Fre- 
quent '  mud  rushes '  occurred  suddenly,  without  the  least  warn- 
ing, and  filled  up  hundreds  of  feet  of  tunnel  in  a  few  minutes, 
the  workmen  being  sometimes  caught  in  the  moving  mass. 

"  It  became  evident  that  the  method  of  working  was  danger- 
ous, the  men  sometimes  being,  when  a  mud  rush  took  place, 
either  shut  in  or  buried  in  the  mud  coming  from  the  opposite  end 
of  the  mine.  It  was  decided,  therefore,  to  work  the  mines  from 
one  side  only,  and  to  have  the  offsets  to  the  rock  connected  one 
with  the  other  at  as  few  points  as  would  be  consistent  with  the 
ventilation  of  the  working  faces.  Main  tunnels  are  driven  (about 
100  ft.  apart)  across  the  crater  upon  its  longer  axis,  and  at  right 
angles  to  these  small  tunnels  are  driven  out  every  30  ft.  until 
they  reach  the  hard  rock  on  the  south  side  of  the  mine.  These 
tunnels  are  widened,  first  along  the  rock,  until  they  connect  one 
with  another,  and  at  the  same  time  the  roofs  or  backs  are  stoped 
up  until  they  are  within  a  few  feet  of  the  loose  ground  above, 
thus  forming  long  galleries,  filled  more  or  less  with  blue  ground, 
upon  which  the  men  stand  when  drilling  holes  in  the  backs.  The 
working  levels  were  at  first  30  ft.  apart  vertically,  but  for  greater 
economy  the  distance  was  soon  changed  to  40  ft. 

"The  broken  blue  ground  in  the  galleries  is  taken  out,  as  a 
rule,  before  there  are  any  signs  of  the  roof  giving  away.  At  times 
this  is  impossible,  and  the  roofs  cave  upon  the  broken  ground, 
and  the  blue  ground  is  covered  with  (barren)  reef."  Figs.  113 


WORKING  DANGEROUS  GROUND 


251 


and  114  show  the  arrangement  of  cross-cuts  and  drifts  and  the 
manner  of  stoping  under  the  conditions  described. 

"  As  the  roof  caves  or  is  blasted  down,  the  blue  ground  is 
removed,  and  the  loose  reef  lying  above  it  comes  down  and  fills 


Plan  and  Vertical  Section  in  Stope  Kimberley  Diamond  Mine. 


Stopes  Connected 


FlG. 114 

the  gallery.  Tunnels  are  often  driven  through  the  loose  reef, 
and  the  blue  ground  which  has  been  cut  off  and  buried  by  debris 
is  taken  out;  but  it  is  sometimes  left  for  those  working  the  next 
level  below  to  extract. 

"  After  the  first '  cut '  near  the  rock  is  worked  out,  another  cut 
is  made,  and  in  this  manner  the  various  levels  are  worked  back, 


252  TIMBERING  AND  MINING 

the  upper  level  in  advance  of  the  one  below,  forming  terraces  as 
shown  in  the  accompanying  sketch.  The  galleries  are  not  sup- 
ported in  any  way  with  timbers,  but  all  tunnels  in  soft  blue 
ground  are  timbered  with  sets  of  two  props  and  a  cap  of  round 
timber,  and  are  covered  with  inch  and  a  half  lagging.  Soft  blue 
ground  is  drilled  with  jumper-drills  sharpened  at  both  ends. 
In  hard  blue  ground  drills  and  single-hand  hammers  are  used. 
The  native  workers  become  very  skilful  in  both  methods  of  drill- 
ing, and  do  quite  as  much  work  as  white  men  would  do  under 
similar  conditions." 


CHAPTER  XXVII 

THE   DELPRAT   METHOD   OF    STOPING    WITHOUT 

TIMBERS 

G.  D.  DELPRAT,  in  "  Transactions  of  the  American  Institute 
of  Mining  Egnineers,"  Vol.  XXI,  describes  a  method  of  stoping 
a  large  body  of  ore  in  Spain  in  which  no  timber  was  employed. 
The  ore  body  was  500  ft.  long  and  from  20  to  75  ft.  wide,  the  aver- 
age being  32  ft.  The  lode  is  nearly  vertical  —  about  75°.  A 
main  extraction  shaft  was  sunk  in  the  hanging-wall,  some  distance 
from  the  vein  at  the  surface,  and  approaching  it  in  depth.  A 
pumping  shaft  was  also  sunk  in  the  hanging,  some  distance  from 
the  main  shaft.  The  lode  was  divided  into  floors  65  ft.  apart. 
From  the  extraction  shaft  galleries  were  driven  at  every  floor, 
cross-cutting  the  lode  entirely.  Where  these  galleries  reached 
the  ore,  narrow  galleries  were  driven  east  and  west,  following 
the  hanging-wall  along  all  the  sinuosities  of  the  lode  and  deter- 
mining its  shape.  From  these  galleries,  again,  cross-cuts  were 
driven  through  the  lode  every  33  ft.  After  learning  the  shape 
of  the  lode,  a  drift  was  run  in  the  hanging-wall  at  an  average 
distance  of  15  ft.,  and  from  the  drift  cross-cuts  were  driven  toward 
the  lode  at  regular  intervals  of  33  ft.  The  drift  was  equipped 
with  track  and  used  as  an  extraction  gallery.  It  was  found  that 
the  drift  along  the  hanging-wall  itself  was  not  suited  to  use  as  an 
extraction  gangway,  as  it  required  constant  timbering.  Both  walls 
of  the  lode  are  slate  and  all  workings  in  it  required  close  timbering. 

When  the  cross-cuts  from  the  majn  hanging-wall  gangway 
had  reached  the  foot-wall,  they  were  filled  with  rock  carefully 
piled  up,  and  new  cross-cuts  were  then  driven  alongside  the  first 
ones.  These  were  filled  up,  and  again  new  ones  were  made  and 
filled,  and  so  on,  until  a  slice  of  ore  had  been  removed  over  the 
whole  length  and  width  of  the  deposit.  All  the  galleries  and  cross- 
cuts had  a  uniform  width  of  6  X  6  ft.,  so  that  the  height  of  the  first 
slice  removed  was  6  ft.  When  this  had  been  accomplished,  the 
gallery  along  the  hanging-wall  also  was  filled  with  waste,  except 

253 


254  TIMBERING  AND  MINING 

at  the  cross-cut  connecting  with  the  main  gangway  out  in  the 
hanging-wall.  At  this  point  a  mill-hole  was  constructed  by  care- 
fully building  a  rock  wall  around  it. 

When  the  first  slice  had  been  removed  and  the  entire  excava- 
tion filled  with  stone  placed  by  hand,  as  above  explained,  a  new 
hanging-wall  drift  was  run  directly  over  the  first,  following  the 
wall,  and  from  this  a  new  series  of  cross-cuts  was  driven,  start- 
ing immediately  above  those  first  driven  and  opposite  the  mill- 
holes  in  the  drift  on  the  wall.  These  new  cross-cuts  in  turn  were 
solidly  filled  with  waste,  and  other  cross-cuts  were  driven  beside 
them  and  filled.  While  the  first  slice  had  been  broken  out  of 
the  solid  ore  body,  the  slice  next  above  was  under-cut  over  its 
entire  area;  in  fact,  it  was  resting  on  the  filling.  This  made  the 
blasting  very  much  cheaper,  so  that  while  the  contract  price  paid 
the  miners  for  the  first  slice  was  50  cents  per  ton,  it  was  only 
25  cents  on  the  next  slice  above.  The  first  cross-cuts  driven 
through  the  solid  ore  body  cost  76  cents  per  ton  of  ore,  while 
the  secondary  cuts,  which  were  only  widening  out  the  first  ones, 
cost  42  cents  per  ton  of  ore.  These  figures  show  the  advantage 
of  having  free  sides  for  the  working  faces  —  an  advantage  not 
obtained  in  the  pillar-and-stall  method. 

After  the  second  slice  has  beeen  removed,  a  third  is  taken  out 
in  exactly  the  same  way,  and  so  on,  until  the  whole  lift  of  65  ft. 
has  been  removed.  Several  levels  were  being  worked  in  this 
manner  at  one  time,  so  that  ore  production  was  not  limited.  No 
new  galleries  nor  cross-cuts  were  started  until  those  adjoining 
had  been  properly  filled  in.  As  the  slicing  proceeded  upward, 
the  mill-holes  were  carried  up  by  walling  up  the  opening. 

The  rock  used  for  filling  was  quartzite,  quarried  at  the  surface 
in  the  vicinity,  and  was  delivered  by  tramway  at  the  collars  of 
two  shafts  sunk  in  the  foot-wall  for  the  purpose  of  delivering 
stone  to  the  stopes.  The  rock  is  lowered  in  stone-boats,  that  for 
the  fourth  level  being  taken  off  at  the  third  and  trammed  through 
the  extraction  gallery  on  that  level  and  sent  below  through 
winzes,  falling  almost  at  the  point  that  it  is  to  be  used.  As  the 
slicing  proceeds,  these  winzes  are  filled  up,  while  the  ore  chutes 
grow  larger  as  stoping  continues  upward.  The  winzes  are  cut  at 
the  hanging-wall  side,  are  3  ft.  square,  and  are  securely  timbered. 
No  smalls  are  used  in  filling,  only  big  stone  being  employed.  A 
stope  65  ft.  high  does  not  settle  more  than  6  in.  when  properly  filled. 


CHAPTER  XXVIII 
HEAD-FRAMES 

BY    GEORGE    SYDNEY    BINCKLEY    C.  E. 

AN  important  element  in  the  working  equipment  of  a  mining 
shaft  is  the  Head-Frame,  or  Gallows  Frame,  as  it  is  often  called. 

In  almost  every  mining  district  a  great  range  may  be  seen  in 
the  variety  and  size  of  the  head-frames,  from  the  simple  tripod  of 
the  prospector  or  small  " leaser"  to  the  towering  structures  of 
timber  or  steel  that  rise  over  the  deep  shafts  of  great  mines.  Yet 
in  spite  of  all  this  variation  in  magnitude  and  type,  the  prin- 
ciples underlying  the  correct  design  of  the  head-frame  are  the 
same,  be  the  structure  large  or  small. 

Although  the  mathematical  elements  involved  in  the  design 
of  a  head-frame  are  simple  in  the  extreme,  no  important  part  of 
the  equipment  of  the  mine  has  been  so  slighted  by  the  engineer 
as  this.  Hardly  a  mining  camp  can  be  found  that  does  not 
exhibit  several  examples  of  large  and  expensive  head-frames 
designed  with  a  total  disregard  for  the  real  nature  of  the  stresses 
that  they  are  intended  to  support. 

The  essentials  in  the  design  of  a  head-frame  are  : 

1st.  Strength.  —  This  may  best  be  assured  by  the  distribution 
of  the  materials  of  construction  along  the  lines  of  the  stresses  to 
be  resisted. 

2d.  Stability.  —  This  may  best  be  secured  by  giving  the  struc- 
ture as  a  whole  the  pyramidal  form,  by  the  avoidance  of  eccen- 
tricity of  stresses  in  the  structure,  and  the  provision  of  sufficient 
area  of  base,  within  which  the  resultant  of  the  working  stresses 
shall  fall. 

3d.  Economy  in  construction.  —  This  will  follow  adherence  to 
the  rules  which  will  be  observed  in  securing  strength  and  stability 
to  the  structure  as  outlined  above,  for  the  materials  of  construc- 
tion distributed  along  the  lines  of  stress  will  be  employed  in  the 
resistance  of  those  stresses  with  the  highest  degree  of  efficiency. 

255 


256  TIMBERING  AND  MINING 

The  working  stresses  in  a  head-frame  (aside  from  the  lateral 
stresses  introduced  in  a  vertical  frame  when  self-dumping  skips 
are  employed,  and  those  due  to  the  weight  of  the  skip  in  the  case 
of  an  inclined  shaft)  are  transmitted  through  the  hoisting  rope 
to  the  sheaves  and  their  bearings,  thence  through  the  members 
of  the  supporting  structure  to  the  foundations. 

The  strain  on  the  rope  is  the  same  on  both  sides  of  the  sheave, 
and  the  direction  of  the  strain  is  along  the  center  line  of  the  rope. 
The  amount  of  weight  on  the  sheave  bearings  will  vary  with  the 
angle  between  the  center  of  the  rope  leading  to  the  hoist,  and 
that  from  the  sheave  to  the  shaft.  For  example,  if  the  rope  led 
straight  up  from  the  shaft  to  the  sheave,  and  straight  down,  ver- 
tically, from  the  sheave  to  the  hoisting  engine  drum,  the  weight 
on  the  sheave  bearings  would  be  double  that  of  the  cage  and  its 
load,  while  if  the  angle  between  the  center  lines  of  the  rope  as 
described  above  is  90°  —  a  right  angle  —  the  weight  supported  by 
the  sheave  bearings  will  be  but  1.41  times  the  weight  carried  by 
the  rope,  and  if  the  angle  between  the  ropes  be  120°  the  weight 
supported  by  the  sheave  bearings  will  be  equal  to  the  pull  on  the 
rope.  In  other  words,  the  weight  supported  by  the  sheave  bear- 
ings is  equal  to  the  pull  on  the  rope  (or  weight  of  cage,  load,  and 
rope  in  a  vertical  shaft,  or  these  weights  multiplied  by  the  sine  of 
the  angle  of  the  shaft  from  the  horizontal  in  the  case  of  an 
inclined  shaft)  multiplied  by  twice  the  cosine  of  half  the  angle 
between  the  rope  leading  from  the  sheave  to  the  hoisting  engine 
and  that  from  the  sheave  to  the  cage  in  the  shaft. 

The  direction  of  the  pressure  on  the  sheave  due  to  the  tension 
on  the  rope,  supporting  the  cage  and  its  load  on  one  end,  and 
attached  to  the  winding  drum  of  the  hoist  on  the  other,  is  in  the 
vertical  plane  only  when  the  vertical  angle  of  the  rope  leading  to 
the  hoist  is  the  same  as  that  leading  from  the  sheave  to  the  shaft. 
The  condition  described  is  seen  in  Fig.  115.  In  all  other 
cases,  the  direction  of  the  pressure  transmitted  from  the  ropes 
through  the  bearings  of  the  sheaves  to  the  supporting  structure 
must  be  in  other  than  a  vertical  plane. 

In  all  cases,  the  direction  of  the  pressure  on  the  supporting 
structure  lies  midway  between  the  center  lines  of  the  ropes  lead- 
ing from  the  sheave  to  the  cage  and  from  the  sheave  to  the  wind- 
ing drum  of  the  hoist. 

A  full  understanding  of  these  fundamental  facts  is  necessary 


HEAD-FRAMES 


257 


for  the  proper  consideration  of  the  problem  of  head-frame  de- 
sign, whether  the  structure  is  to  be  large  or  small,  for  light  or 
heavy  duty. 

Reference  to  Fig.  116  will  make  clear  to  the  reader  the 
explanation  given  above  relative  to  the  direction  of  pressure  due 
to  the  tension  on  the  ropes.  It  will  be  seen  in  both  instances 
given,  that  the  resultant  of  these  forces  lies  midway  between  the 
ropes,  whether  the  shaft  be  vertical  or  inclined.  Fig.  115  is  a 
case  where  the  inclined  shaft  is  considered.  Here,  if  the  hoist 
is  so  set  that  the  angle  of  the  rope  is  the  same  on  both  sides  of  the 
sheave,  the  direction  of  the  pressure  on  the  structure  (the  re- 
sultant) will  be  vertical.  It  thus  becomes  entirely  proper  to  make 
the  back  of  the  frame  vertical,  and  to  employ  the  front  for  the 
support  of  the  skip  tracks  and  the  support  of  an  ore  bin  as  shown. 


Compression  Panel 


FIG.  115 


This  makes  an  extremely  simple  and  economical  design  for  a  head- 
frame  for  an  inclined  shaft,  and,  while  cheaper  and  more  compact 
than  the  usual  form,  is  quite  as  safe  and  stable  as  if  the  structure 
were  extended  far  out  toward  the  hoist.  The  hoist  could  in  this 
case  be  set  closer  to  the  frame  without  any  change  in  its  design, 
but  if  set  farther  away,  the  back  bent  would  have  to  be  corre- 
spondingly inclined  so  as  to  fall  in  the  line  of  the  resultant. 

In  engineering,  little  is  to  be  learned  from  success  —  much 
from  failure.  An  error,  to  be  corrected,  must  first  be  recognized. 
In  order  to  make  clear  the  errors  so  common  in  the  ordinary 
type  of  head-frame  so  extensively  employed,  Figs.  117,  118,  119, 
120,  are  introduced. 

In  Fig.  117,  is  seen  a  very  common  form  of  head-frame, 
ordinarily  used  where  the  shaft  is  of  considerable  depth  and  ex- 


258 


TIMBERING   AND   MINING 


traction  heavy.  On  account  of  the  complicated  framing  and  the 
large  number  of  bolts  and  ties  called  for  in  this  design,  the  cost 
of  this  type  of  head-frame  is  generally  heavy.  Obviously,  the 
assumption  upon  which  this  design  is  based  is  that  the  direc- 
tion of  the  pressure  to  be  resisted  by  the  structure  is  in  the 
vertical  plane,  along  the  center  line  of  the  rope  leading  down 
the  shaft.  This  idea  is  strongly  indicated  by  the  position  of  the 
rope  in  the  braced  tower,  and  the  position  of  the  sheave. 


Vertical  Shaft 


Incline  Shaft 


FIG.  116 

The  actual  direction  of  the  pressure  due  to  the  load  on  the 
rope  is,  in  this  diagram,  very  clearly  shown,  and  it  will  be  seen 
that  the  line  of  the  pressure  falls  almost  entirely  outside  of  the 
elaborately  framed  and  braced  four-post  tower,  and  is  taken 
almost  altogether  by  the  back  bracing.  As  a  matter  of  fact,  the 
four-post  tower  could  have  substituted  for  it  a  plain  vertical 
bent  without  sacrifice  of  strength  or  stability. 

In  Fig.  118  is  shown  the  familiar  simple  tripod.  In 
this  case  it  will  be  observed  that  the  direction  of  the  resultant 
is  well  within  the  simple  members  of  the  frame,  and  that  this 


HEAD-FRAMES 


259 


2    I 


260  TIMBERING  AND  MINING 

elemental  form  of  head-frame  is  far  more  correct  in  design  than 
the  ambitious  and  complicated  "four-post"  type. 

A  type  of  the  head-frame  used  to  a  considerable  extent  in 
many  mining  districts  is  shown  in  Fig.  119.  This  type  is 
a  great  improvement  in  stability  over  the  ''four-post"  design,  yet 
its  complicated  bracing  system  should  be  avoided  as  expensive 
and  irrational.  While  in  this  type  the  resultant  of  the  tension 
on  the  ropes  generally  falls  well  within  the  structure,  a  proper 
relation  between  the  strength  of  the  front  and  back  members  of 
the  frame  is  rarely  seen,  and  the  practice  of  placing  the  sheave 
bearings  on  relatively  long  caps  connecting  the  front  and  back 
panels  introduces  a  sequence  of  strains  in  the  bracing  system 
that  extends  throughout  the  structure  to  the  foundation.  This 
fact  makes  necessary  the  very  heavy  bracing  system  always  found 
in  this  type  of  head-frame,  as  its  duty  is  not  alone  to  secure  stabil- 
ity to  the  structure,  but  to  transmit  part  of  the  working  strains  to 
the  foundation  —  a  duty  with  which  the  bracing  system  of  a 
head-frame  is  not  properly  charged. 

Fig.  120  is  a  striking  example  of  the  scant  consideration 
so  often  given  the  nature  and  direction  of  the  stresses  to  be 
resisted  by  a  head-frame.  In  this  case,  although  the  structure 
is  apparently  one  of  the  greatest  stability,  the  line  of  the  resultant 
of  the  tension  on  the  ropes  falls  almost  entirely  outside  the  frame, 
the  stability  of  which  depends  altogether  on  its  own  dead  weight 
and  that  of  the  foundations  to  which  it  is  anchored.  The  example 
from  which  this  diagram  was  made  is  a  very  elaborate  steel  struc- 
ture, and  is  illuminating  in  the  completeness  of  its  contempt  for 
rational  design. 

The  writer  has  made  an  effort,  in  the  typical  design  for  a  large 
steel  head-frame  shown  in  Figs.  121  and  122,  to  avoid  those  errors 
pointed  out  above,  and  to  conform  as  nearly  as  possible  to  both 
the  theoretical  and  practical  requirements  of  head-frame  design. 
In  this  design  (published  first  in  the  Mining  and  Scientific  Press 
of  San  Francisco  several  years  ago)  it  will  be  observed  that  the 
sheave  bearings  are  placed  directly  on  the  end  of  the  main 
compression  members  of  the  structure,  the  intermediate  bear- 
ings being  carried  by  a  beam  of  such  depth  and  stiffness  that 
deflection  under  load  will  be  negligible.  The  two  main  columns, 
being  brought  as  close  together  as  possible  at  their  heads,  are 
inclined  laterally,  giving  a  relatively  wide  base  and  consequent 


HEAD-FRAMES 


261 


stability.  The  position  in  which  the  sheave  bearings  are  placed 
insures  the  direct  transmission  of  the  working  stresses  through 
the  main  compression  members  to  the  foundation  without  eccen- 
tricity, hence  the  efficiency  of  the  metal  in  the  columns  is  maxi- 
mum. 

On  account  of  the  fact  that  the  working  resultant  of  the  tension 
on  the  ropes  lies  practically  within  the  compression  member  itself, 


FIG.  121 


FIG.    122 


the  function  of  the  forward  or  shaft  side  of  the  frame  is  merely 
to  hold  the  heavy  back  panel  in  position,  and  give  the  necessary 
stability  to  the  structure.  This  bracing  may  be  very  light,  for 
no  working  strains  whatever  are  transmitted  through  the  bracing 
system,  except  those  insignificant  strains  that  may  arise  from  the 
dumping  of  skips  if  these  are  used. 

The  design  exemplified  in  Fig.  121  probably  represents  the  ulti- 


262 


TIMBERING  AND  MINING 


mate  form  of  greatest  economy  of  material  in  the  construction 
of  a  large  steel  head-frame  for  a  vertical  shaft. 


An  adaptation  of  the  same  design  is  seen  in  Figs.  123  and  124. 
This  is  a  typical  design  for  a  fifty -foot  head-frame  of  wood  con- 
struction, and  embodies  the  same  characteristics  as  those  of  the 
steel  head-frame  described  above.  An  unconventional  method 


HEAD-FRAMES  263 

of  construction,  however,  is  suggested  in  this  design,  which  the 
writer  believes  will  be  found  of  value. 

It  will  be  seen  that  the  timbers,  instead  of  being  solid,  are  of 
a  laminated  structure,  built  up  of  two-inch  plank  spiked  together 
in  such  a  way  that  the  bracing  system  is  built  in  with  the  main 
compression  members,  requiring  for  the  most  part  no  rods,  bolts, 
or  ties,  to  secure  a  very  solid  and  strong  frame. 

The  advantages  offered  by  the  proposed  method  of  construc- 
tion are  several.  Long  timbers  are  not  necessary,  as  members 
of  any  length  may  be  built  up  out  of  comparatively  short  plank. 
Such  timber  or  plank  as  would  be  needed  for  the  construction  of 
even  a  very  heavy  head-frame  of  this  type  can  be  much  more 
readily  obtained  than  long  dimension  timber,  and  at  much  lower 
cost.  It  is  also  true  that  such  a  frame  as  that  shown  in  Figs. 
123  and  124  will  be  stronger  than  one  framed  of  heavy  timber, 
while  it  can  be  successfully  built  with  less  highly  skilled  labor. 

It  is  obvious  that  many  variations  in  the  detail  of  construc- 
tion and  design  will  present  themselves  to  the  engineer  during 
the  working  out  of  field  drawings  for  the  actual  construction  of 
such  a  head-frame,  but  the  general  principle  shown  can  be  fol- 
lowed with  full  confidence  in  the  strength  and  permanency  of  the 
completed  structure,  whether  it  be  large  or  small. 

An  earlier  design  by  the  writer  is  seen  in  Fig.  125,  which  is  an 
illustration  of  the  High  Ore  head-frame,  Butte,  Montana.  This, 
and  another  of  equal  height  to  the  center  of  the  sheaves  for 
the  Diamond  Shaft,  was  designed  by  the  writer  in  1898,  and 
although  not  so  advanced  as  that  shown  in  Fig.  121  embodies 
most  of  the  principles  elucidated  above.  It  is  one  hundred  feet 
high  to  the  center  of  the  sheaves,  and  carries  a  live  load  on  the 
ropes  of  about  sixty  thousand  pounds.  The  hoisting  engine  (also 
of  the  writer's  design)  is  of  the  horizontal,  double,  direct-acting 
type,  with  cylinders  30  inches  diameter  by  six  feet  stroke,  working 
under  a  steam  pressure  of  140  pounds  to  the  square  inch.  The 
duty  of  this  head-frame  is  obviously  very  heavy,  yet  on  account 
of  the  fact  that  the  sheave  bearings  are  carried  directly  on  the 
main  members,  and  the  pyramidal  form  of  the  structure,  it  is 
perfectly  stable  and  free  from  any  vibrations  even  under  full  load 
moving  at  high  speed.  The  relatively  small  base  of  this  head- 
frame  makes  its  stability  still  more  noteworthy,  and  demon- 
strates the  correctness  of  the  principles  followed  in  its  design. 


264 


TIMBERING  AND   MINING 


Two  other  steel  head-frames  in  Butte,  designed  by  the  writer  for 
the  Boston  &  Montana  Co.  and  erected  on  the  Mountain  View 
and  the  Leonard  shafts  of  that  company,  were  eighty  feet  to  the 
center  of  the  sheaves,  and  followed  in  general  the  same  prin- 


FIG.  125 

ciples  of  design  employed  in  the  High  Ore  and  Diamond  head- 
frames.  Yet,  although  perfectly  stable  and  satisfactory  in 
service,  the  writer  is  now  forced  to  consider  them  relatively  crude, 
especially  as  regards  economy  of  construction,  when  compared 
with  those  shown  in  Figs.  121  and  123. 


HEAD-FRAMES  265 

The  head-frame  on  an  important  mine  is  now  such  a  serious 
element  in  the  equipment  that  it  should  receive  the  intelligent 
attention  of  the  designing  engineer,  and  be  no  longer  left  to  the 
tender  mercies  of  the  boss  carpenter,  or  the  well-meant  but  often 
unfortunate  attentions  of  the  mine  foreman. 


INDEX 

PAGE 

Abuses  of  square-set  system    193 

Air  currents,  effect  of,  on  timbers 2,    3,    4,    5,    6 

Alma  mine,  Cal.,  shaft    75,  77 

Angle  braces  in  square-sets 191 

for  side  pressure     191 

Argonaut  Mine,  Cal 55,  75 

Automatic  dumping  devices  at  shafts 64,  72 

winzes 184 

skips  128, 129 

Bacon,  D.  H 166 

Bad  ground 19,  28 

Bailing  by  electrically-operated  skips 51 

Bailing  by  skips  and  tanks 125,  127,  130,  132 

Barrier  Range,  Australia    213 

Bearers  in  shafts    105, 162 

Beaumont,  E.  K 213 

Behr,  Hans  C 126 

Bevel  in  tramming  shaft  sets 75 

Big  Indian  mine,  Mont.,  open  cut  at 135 

Binckley,  George  S 255 

Blasts  fired  electrically 118 

Blasting  holes  in  series   .7 118,  174 

Block  caving  at  Pewabic  mine    172 

Block  holing  at  Homestake 240 

Blocking  out  ground  for  caving  system     174 

Block  system  of  stoping  at  Broken  Hill 213,  223,  224 

Homestake 242 

Blue   lead  of  California 38 

Bolts,  hanging 58 

Breast  boards  in  working  through  running  ground 29,  32 

shaft  sinking 99 

Breasting  posts  and  caps   38 

Bridge,  the  use  of  in  drifting     24,  29 

shaft  sinking     99 

Broken  Hill  Mines,  N.  S.  W.  Australia 193 

block  stoping  at     213,  223,  224 

open-cut  mining  at    226 

stoping  by  slicing  at    222 

underground  open-cut  at 218 

267 


268  INDEX 

PAGE 

Brush  treatment  of  timber 9,14 

Bucket-dumping  devices    64,  72 

use  of  in  sinking 58 

with  valve     127 

Building  of  chutes     170 

Building  up  to  secure  dump 55 

Bulkhead  in  stopes  at  Broken  Hill     219 

Bumper  for  crosshead     61 

skips 71 

Cable  mat  to  protect  shaft  timbers 112 

Cages  in  shafts 53, 1 19, 120 

skips 120 

service,  in  shafts 50 

Caledonia  mine,  South  Dakota   236 

Calico  District,  Cal.,  large  stopes  in - 195 

California  drift  mines,  method  of  working 38,  41 

Capacity  of  shafts   50 

bailing  skips 51 

Caps  and  breasting  posts   38 

replaced  in  position   31 

Cap  sills  in  square-sets   207,  216 

Carbon  dioxide,  effect  of  on  timbers 7 

Care  in  placing  posts  in  drifts 159 

Cave  in  Caledonia  mine    236 

mine  at  Angels,  Cal.  ~ 195 

Caved  ground  working  at  Homestake    238 

Caving  system  at  Iron  Mountain 172 

Centering  drift  sets   18 

Cerro  Prieto  mine,  Sonora.,  Mex.,  mining  at 154 

China,  great  shafts  in 49,  73 

Churn  drill  or  jumper 141 

depth  of  holes  drilled  by 143 

Chutes  for  passing  timbers  underground  203 

in  square-sets 167,  211 

construction  of    170,  211,  214,  235 

device  for  handling  timbers  at  shafts 87 

Cobalt  district,  Ontario 62 

small  shafts  in 63 

Collar  of  shafts 44,  56 

concrete  at    44 

Combination  inclined  and  vertical  shafts 102, 103 

of  round  and  square  timbers  in  sets 200 

Comparative  cost  of  timber  treatments     13 

Compartments,  size  of  shaft 54 

Comstock  lode,  early  mining  on    187 

introduction  of  square-sets  on  188 


INDEX  269 

PAGE 

Comstock  lode,  shafts  on 73^  78 

skips  at    128 

Concrete  at  collar  of  shaft    44 

Connecting  levels  by  raising 161 

in  stoping    184 

Construction  of  square-sets   201 

Continuous  raises  at  Homestake 233 

Cornish  pumps 51 

Correcting  errors  in  placing  shaft  timbers     .  .  .- 92 

Cost  of  stoping  at  Homestake  245 

timber  treatment    13 

Cribbed  shaft,  how  built 48 

Cribs 46,  48 

in  square-sets 193,  221 

surrounding  shafts  in  swelling  ground 109 

"Creeps" 216 

Cross-head  in  shaft  sinking 58 

how  made    59 

bumper  for    61 

Cut  holes,  best  place  for  in  blasting 118 

in  Hoatson  shaft,  Bisbee,  Ariz 118 

Cut  stations  when  sinking    120 

Cutting  and  timbering  stations  at  shafts 119 

stations,  methods  of    120 

Cylinder  treatment  of  timbers 13 

Danger  in  overwinding 72 

of  fire  in  timbered  stopes    217 

Dead  wood -Terra  mine,  stoping  at Vr. 238 

Deep-level  shafts  on  Witwatersrand 104 

Deidesheimer,  Philip .  • 188 

Del  Mar,  Algernon 62 

Delprat,  D.  G 253 

Details  of  framing  shaft  timbers 48,  74,  76,  77,  79 

square-set  system 192 

Detroit  Copper  Co.,  Morenci,  Ariz 45 

Diamond  mines,  South  Africa,  mining  at    247 

Different  styles  of  drift  timbering 17,  18,  183,  227 

head-frames 255 

Disadvantages  of  underhand  stoping 149 

Direction  of  strains  in  head-frames    256 

Distance  piece  for  guides  in  shafts 82 

Divider,  the    80,  83 

Dogs,  iron,  in  shafts .       78 

Douglas  spruce 2,  3,  4,  5,  6 

Drainage  of  shafts    51 

by  bailing    51, 126, 132 


270  INDEX 

PAGE 

Drains  in  drifts,  necessity  for    17 

Draining  wet,  running  ground 28 

Drifts,  drains  in  17 

Drift  sets,  how  centered    18 

lining  up    25 

mines,  timbering  of 38,  41,  159 

timbering  at  Broken  Hill    227 

timbers  crushed  by  pressure 108 

Drifting  and  drift  sets 16,  17,  18,  183,  228 

with  false  set 24 

Drill  holes  in  shaft  sinking 117 

" springing"  for  heavy  charges 143 

Drilling  with  churn  drill     142 

Driving  lagging    18,  24,  28,  29 

Dumping  devices  at  collar  of  shafts    64,  72,   128 

winzes 184 

Eagle-Shawmut  mine,  Cal 155 

Early  mining  at  the  Broken  Hill  mines 214 

Comstock  mines 187 

Homestake    236 

Economy  in  head-frame  construction 255 

Effect  of  moisture  on  timber    .  .  .  .  '. 2,3,4,5,6 

air  currents  on  timber 2,  3,  4,  5,  6 

carbon  dioxide  on  timber 7 

Elkhorn  mine,  Mont.,  remarkable  timbering  in   188 

Ellison  shaft,  Homestake  229 

Empire  mines,  Grass  Valley,  Cal 2 

Evolution  of  square-set  timbering    188 

Extension  tracks  for  shaft  sinking   113 

wheels  on  skips 71 

Results  derived  from  experiments  in  treating  timber    13 

Face  boards  in  working  through  running  ground 29,  32 

sinking  shafts 99 

False  set,  drifting  with   24 

Fenders  to  protect  shaft  timbers Ill 

Filling  at  Broken  Hill     216 

Homestake 140 

in  stopes 140,  168,  214 

for  stopes,  how  obtained     160,    18J ,   254 

waste  used  for     152 

Finlay,  J.  R 154, 156 

Fire,  danger  of  in  square-sets    217 

Firing  blasts  by  electricity 118 

Flat  veins,  method  of  stoping 158 

"Flying  Fox"  at  Broken  Hill 226 


INDEX  271 

PAGE 

Foot  blocks  in  drift  sets 29 

Forepoling  in  shaft  sinking    99 

Framing  shaft  timbers 47,  73,  75 

for  top  pressure    198,  199 

square-set  timbers 197 

timbers  for  side  pressure 198 

Fungus  growth  on  timbers  in  mines 2,  3,  4,  5,  6 

Gallows  frames 255 

Government  experiments  in  timber  treatment .   8,  15 

Grizzly  in  open  cut    134 

ore  pass    137,  232 

Guides  in  shafts  59,  61 

Gwin  mine,  California     178,  183 

shaft 55 

Half  hitch  and  timber  hitch .-.-, .       89 

Hammer  drill,  pneumatic 170,  240 

Hampton,  E 5 

Handling  powder  underground 123 

timbers  in  raises   ' 180 

shafts     58,  87 

Hanging  bolts  in  shafts 57,  78 

Haste  in  bad  ground  a  mistake 28 

Hayward,  Alvinza  205 

system  of  square-sets 205 

Head-frame  on  framework 55 

rational  design  of     255 

steel    ~_^. 53,  263 

Height  of  shaft  stations    . 122,  229 

Hewn  timbers 48 

High  ore  mine,  Butte,  Mont.,  steel  head-frame  at     264 

Homestake,  block  system  of  stoping  at   242 

continuous  raises  at 233 

early  mining  at 236 

filling  stopes  at -. 240 

mills     235 

mine,  South  Dakota 120,  123,  136,  229,  238,  242 

mining  at 229 

recovering  caved  ore  at 236 

shaft  stations  at     229 

stoping  without  timbers 238 

Huddlestone,  Thos 157 

Hydraulic  jack,  usefulness  of  in  mine 31,  58 

Improper  head-frame  design    255 

Inclined  shafts 55,  69,  71,  76,  93,  103,  107,  113,  115,  124,  129 


272  INDEX 

PAGE 

Inclined  shafts,  bucket  dumping  devices  at   64,  72 

in  hard  rock 115 

Inverted  rails  for  track  extension 114 

Iron  dogs  in  shaft  timbers 78 

Iron  Mountain,  caving  system  at    172 

Jack-knifing  of  sets 22 

screw  in  mines 31 ,  58 

Joint  for  post  and  sill 23 

Jumper  or  churn  drill 141 

Kennedy  east  shaft 55,  99,  101 

Kimberley  diamond  mines,  mining  at    247 

Kinds  of  timber  used  in  mining    1 

Knots,  some  useful    88,  89 

Ladders  in  raises   163 

Lagging,  driving 18,  24,  29 

in  square-sets 214,  240 

on  floors  of  stopes 242 

Laminated  construction  of  head-frames 263 

Large  ore  bodies,  mining  by  open-cut  method 133,  144,  227 

stoping 187,  207,  209,  212,  238,  242,  254 

tonnage  hoisted  through  shafts    50 

Lateral  stresses  in  head-frames 256 

Leggett,  Thomas  H 104 

Levels  connected  by  raises 161 

connecting,  method  of 184 

Life  of  timbers  underground    .' 2,  3,  4,  5,  6,  206,  214,  216 

Limitations  of  square-set  system  in  mining    195 

Lining  up  drift  sets  25 

shaft  sets     93 

Location  of  shaft  with  reference  to  subsequent  operations 43 

Long  wall  system  of  mining 160 

Lord,  Elliott     187 

Machine  shops  underground 122 

Main  gangwags  in  country  rock    179 

Makeshift  methods  unadvisable 57 

Making  a  cross-head    59 

Method  of  cutting  stations  at  shafts 120,  123,  124 

framing  drift  sets    17,  18,  183,  226 

~  square-sets 197,  209 

Method  of  mining  at  Broken  Hill 193,  212,  223,  225 

Homestake 233,  239,  242 

Utica-Stickle 208 

Yellow  Aster  .  137 


INDEX  273 

PAGE 

Method  of  mining  at  Zaruma,  S.  A 156 

by  Longwall  system 160 

in  open  cuts    133,  144,  226 

obtaining  filling  from  walls     182 

stoping 148, 154 

flat  veins 185 

in  weak  walls    166 

slices 156,  222 

swelling  ground    178 

without  timbers 172,  238,  253 

timbering  at  Gwin  mine 183 

Utica  mine    208 

Wildman  mine 211 

working  drift  mines  in  California    38,  41 

Mexico,  great  shafts  in 49,  73 

Mill  holes  in  open  cuts    134, 137 

Mine  drainage 17,  28,  125,  127,  130,  132 

Mine  drainage  and  pumps    126 

Mine  models,  usefulness  of     •.  .     243 

timbering,  methods  of 40 

Mining  at  Broken  Hill,  N.  S.  W 212 

Cerro  Prieto,  Mex 154 

the  Homestake     229 

Kimberley 247 

Angels,  Cal 208 

Yellow  Aster 137 

by  caving  system 172 

Glory  Hole  method    133,  136,  143 

Longwall  method     •-.- 160 

Minnesota  iron  mine,  stoping  in    166 

Mistakes  in  use  of  square-sets 193 

Modifications  of  square-set  system .201,  203 

Moisture,  effect  of  on  timbers    2,  3,  4,  5,  6 

Mother  lode  of  California 19,  55,  75,  106,  178,  195,  209 

Mount  Morgan  mine,  Australia 139 

Lyell  mine,  Tasmania 147 

Necessity  for  drains  in  drifts  17 

New  Almaden  mine,  Cal 5 

Norris,  R.  V 34 

Oak,  use  of  in  mines 3 

O'Brien,  W.  S 239 

Open  cut  Big  Indian  mine 135 

Broken  Hill  mine    226 

churn  drill  in  141,  144 

Homestake  mine 235 


274  INDEX 

PAGE 

Open  cut  Yellow  Aster  mine    137 

Wasp  No.  2  mine,  South  Dakota     158 

method  of  mining 133, 144 

mill  hole  in 134 

steam  shovel  in 144 

underground  at  Broken  Hill 218 

stope    151 

tank  treatment  of  timber     10,  13 

Ophir  mine,  Comstock  lode    187,  194 

Ore  chutes  in  square-sets 176,  211 

Ore-bins  beneath  levels 120 

Oregon  pine    1,  2,  3,  4,  5,  6,  216 

Ore  pockets  under  levels 120 

Overhand  stoping    150 

stope  carried  to  surface 151 

Overwinding,  danger  in    72 

Oneida  mine,  Cal 5,  21,  55,  101 

Patton,  W.  H 193, 214 

Permanent  hoisting  plant 52 

Pewabic  mine,  caving  system  at     172 

Pine,  varieties  of,  used  in  mines 2,  3,  4,  5,  6 

Placing  shaft  timbers  in  position 89,  95 

sills  in  square-sets    202 

stope  timbers  in  position    201 

Platforms  in  drift  sets,  temporary 26 

shafts,  temporary 91 

stopes,  temporary    203 

Pneumatic-hammer  drill 170,  240 

Policy  for  preservation  of  timber   14 

Position  and  direction  of  drill  holes  in  shaft  sinking 117 

of  temporary  hoisting  plant 52 

Possibilities  of  timber  treatment 11 

Post  and  sill  joint    23 

Posts,  care  necessary  in  placing    159 

perpendicular  to  roof 21 

Powder  underground 124 

Premium  system 46 

Preservative  treatment  of  timber 8, 14 

Principles  underlying  methods  of  timbering  16 

Prospectors  as  engineers 43 

Prospecting  shafts 43 

Protection  of  shaft  timbers    Ill 

Pumps,  Cornish    ' 51 

i 

Raises,  continuous 233 

divided 161 


INDEX  275 

PAGE 

Raises  for  connection  of  levels    161 

ladders  in 163 

how  made    161 

ventilation  of    165 

Raising,  progress  of  at  Homestake     234 

Redwood  as  mine  timber 2,   3,   4,  5,   6 

Reinforcing  square-sets 193 

Remarkable  stope  in  Elkhorn  mine,  Mont 188 

Repairing  shafts 116 

Resultant  strains  on  sheave  in  head-frame   256,  259 

Results  of  experiments  in  treatment  of  timber 13 

Robbins,  Frank    69 

Ross,  John,  Jr 2 

Ross,  Gilbert  McM 4 

Rowlands,  Richard 29 

Running  ground 28 

driving  through    77T 29 

sinking  through    97 

Saddle  wedges,  use  of 31 

Sagging  caps,  how  replaced 31 

Scarcity  of  timber,  effect  of  on  mining    154 

Selection  of  timber    47 

Self-dumping  skips    128, 129 

Service  cage  in  shaft  51 

Shaft  building  by  raising 161,  163 

compartments,  size  of 54 

Ellison,  at  Homestake 229 

repairing --, 116 

sinking,  drill  holes  in 117 

timbers,  placing  in  position    89,  93 

protection  of     Ill 

Wildman,  Cal 107 

Shafts,  bucket  dumping  devices  at 64,  72,  128 

combination  vertical  and  inclined 102,  103 

concrete  at    44 

cribbed 46,  48 

guides  in    59,  61 

handling  timbers  in  85 

large  tonnage  hoisted  through     50 

location,  kind  and  size  of 43 

on  Comstock  lode 73 

size  and  division  of    49. 

without  timbers 46,  47 

working 43 

Side  pressure,  angle-braces  for    191 

framing  timbers  for    198 


276  INDEX 

PAGE 

Sills,  employment  of  in  drifts    22 

stopes 190,  201,  207,  211,  214 

placing  in  square-sets    202 

Sinking  shafts,  extension  tracks  for 113 

ladders  for 115 

through  running  ground 97 

with  cross-head  and  bucket    58 

Size  and  division  of  shaft  compartments 54 

of  timbers  determined  by  experience 20 

stopes  depend  on  ground 203 

Skips,  automatic  dumping 128, 129 

bailing  with     125,  127,  130,  132 

in  inclined  shafts 58 

versus  Cages 120 

with  valves • 127 

Slicing  at  Broken  Hill 221 

Zoruma    156 

Slides  for  timber  in  square-sets     203 

Sloping  stopes  at  Broken  Hill 222 

Some  useful  knots 88,  89 

South  Eureka  mine,  handling  timbers  at 180 

Spiked  plank  in  drift  sets 17,  18 

Spliced  wall  plate 81,  84 

Sprags,  denned 22 

in  square-sets    22,  21 1 

use  of 22,  211 

Springing  drill  holes  for  blasting 143 

at  Wasp  No.  2  mine    158 

Square-sets,  construction  of  in  stopes 201 

Hayward  system 205 

Square-set  system,  abuses  of 193 

invention  of 188 

limitations  of    195 

method  of  framing  timbers  for    197 

modifications  of 201 

wall  plates  in    191 

Starr,  Geo.  W 2 

Stations  at  shafts 119 

Homestake  shafts  229 

height  of,  at  shafts  122,  220 

inclined  shafts 124 

vertical  shafts    123 

Steam  shovel  at  Bingham,  Utah 147 

Ely,  Nev 146' 

Granby,  B.  C 145 

in  open  cuts    144 

Mesabi  Range .      145 


INDEX  277 

PAGE 

Steel  head-frame,  High  Ore  mine,  Butte,  Mont 264 

Old  Dominion  mine,  Globe,  Ariz 53 

mine  timbers 34,  37 

Stope,  caving  of  at  Angels,  Cal 195 

chutes  in    167 

connecting  levels  in 184 

"creeps"  in 216 

filling  in     168 

size  of 194, 195 

superficial  area  of 194,  195 

without  timbers 238,  253 

Stoping  at  Broken  Hill     216 

Homestake,  cost  of    245 

Utica  mine 208 

by  block  system,  Broken  Hill    . 212 

at  Homestake    242 

in  diamond  mines,  South  Africa    247 

swelling  ground    178 

walls  for  filling . '. 181 

weak  walls 166 

methods 148, 160 

large  ore  bodies    187 

early  difficulties   187 

overhand     150 

underhand 148,  149 

without  timbers  at  Homestake 233 

in  Spain    253 

Strain  on  hoisting  rope     256,  257,  258,  261 

Stulls,  use  of  in  small  shafts    62 

Sump  tanks  under  levels    ~TT 125 

Swelling  ground 19,  106,  180 

on  mother  lode     106,  180,  183 

sinking  through    109 

stoping  in    178 

Tanks,  bailing 125,  127,  130,  132 

Tanks  under  levels 125 

Template,  the 85 

how  made    85 

Temporary  hoisting  plant 52 

platforms  in  drift  sets 26 

stopes 203 

The  straight-edge 94 

bowline ^ 89 

cable  mat  to  protect  shaft  timbers  112 

cross-head,  how  made . 58,  60 

divider 80,  83 


278  INDEX 

PAGE 

The  template    85 

timber  hitch     89 

truck    85 

Timber  chutes  in  stopes   203 

crushed  by  pressure 108 

framing  machine    199 

gang 27 

head-frames 262 

selection  of    47 

truck,  the    85 

effect  of  air  currents  on  1,  2,  3,  4,  5,  6,  216 

handling  at  shafts    85 

hitch 89 

preservation  of 8 

treatment  of 9 

placing  in  position  in  shafts 89,  93 

stopes     201 

used  in  mines    1 ,  2,  3,  4,  5,  6,  214 

Timbering  at  Broken  Hill , 212,  225 

Gwin  mine 178, 183 

Homestake    229 

Utica  mine    208 

drift  mines . . ., 38,  41 

stations  at  shafts 119 

Top  pressure,  framing  for 198 

Topography  about  shaft  important    53,  55 

Treatment  of  timber  in  open  tanks 10 

cylinders    13 

by  brush    9 

possibilities  of 11 

Treadwell  mine,  Alaska    .  .  .' 244 

Tuffs,  large  stopes  in 195 

Types  of  head-frame  construction    259 

stations  at  inclined  shafts 124 

vertical  shaft     123 

Utica-Stickle  mine,  Angels,  Cal 55,  86,  178,  208 

handling  timbers  at  86 

stoping  at  208 

Usefulness  of  mine  models  ^ 243 

square-set  in  extracting  large  ore  bodies 191 

hydraulic  jack  in  mines 31 

Underground  machine  shops 122 

open  cut,  Broken  Hill 218 

working  powder  in 123,  124 

Underhand  stoping    149 

Underlying  principles  in  timbering 16 


INDEX  279 

PAGE 

Unusual  methods  of  stoping    154 

Uren,  Charles   155 

Valve  buckets  and  skips 127 

Varieties  of  timber  used  in  mines    1,  2,  3,  4,  5,  6,  214 

Ventilation  of  raises  important   165 

at  Homestake 234 

Vertical  shafts,  bucket  dumping     64 

devices  at    64,  72 

placing  timber  in 89 

Wall  plates  in  shafts   81 

square-sets 191 

Walls,  weak,  stoping  in 166 

Wasp  No.  2  mine,  mining  method  at 158 

Waste  for  filling 152 

Weber,  Frank  F 5 

Wedges,  importance  of  199 

must  be  kept  tight 47 

Wildman  mine,  Cal 4, 107 

Williams,  Gardner  F.    >. 247 

Winzes,  dumping  devices  at 184 

Witwatersrand,  deep-level  shafts    104 

Working  caved  ground  at  the  Homestake 237 

shafts 43 

stresses  in  head-frames 256 

Yates,  Bruce  C 244 

Yellow  Aster,  mining  at  137 

square-sets  in 195 

Yellow  pine 2,  3,  4,  5,  6 

Zaruma,  Ecuador,  S.  A.,  mining  at    156 


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